Quan sát mã javascript sau var n1

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Trong JavaScript, các phép toán số học luôn được thực hiện ở dạng dấu phẩy động có độ chính xác kép [KHÔNG phải là số nguyên]. Nghĩa là,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

ECMAScript 2016 [ES7] giới thiệu toán tử số mũ [

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Trước ES7, bạn phải sử dụng chức năng tích hợp sẵn

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Đây là những toán tử tay ngắn để kết hợp hai hoạt động

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

• parseInt[str], parseFloat[str]. Phân tích cú pháp

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  016 cho đến chữ số đầu tiên và trả về số;
• môn Toán. vòng[số], Toán. sàn[số], Toán. trần nhà [số]
• môn Toán. ngẫu nhiên[]. Tạo một số ngẫu nhiên giữa 0 [bao gồm] và 1 [độc quyền]
• isNaN[str]. trả về true nếu

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  016 không phải là số. Ví dụ,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  07Thật thú vị khi lưu ý rằng JavaScript không có các chức năng đối ứng như

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  393,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  394
• Số[str]. Trả về số đại diện bởi

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  040, hoặc

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  391. Cho rằng tên hàm này bắt đầu bằng chữ hoa, bởi vì đây là thao tác truyền kiểu
• toFixed[decimalPlaces]. Trả lại số/chuỗi này về số vị trí thập phân đã cho. Ví dụ,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  08

Loại

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

331, Chữ & Hoạt động

Một

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Không giống như Java/C/C++, nhưng giống như các thuộc tính của HTML/CSS, bạn có thể sử dụng dấu ngoặc đơn hoặc dấu ngoặc kép cho

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

JavaScript là kiểu động và tự động thực hiện chuyển đổi kiểu. Khi giá trị

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Nếu cả hai toán hạng của toán tử

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Để chuyển đổi một số

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Hãy lưu ý rằng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn cũng có thể sử dụng hàm

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

• chiều dài. e. g. ,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1140 trả về độ dài của chuỗi

• Đến trường hợp trên[]. trả về chuỗi chữ hoa
• toLowerCase[]. trả về chuỗi chữ thường
• charAt[idx]. trả về ký tự ở vị trí

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1141. Chỉ số bắt đầu từ 0. Có thể sử dụng chỉ mục phủ định, tính từ cuối chuỗi
• chuỗi con [bắt đầuIdx, endIdx]. trả về chuỗi con từ

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1142 [bao gồm] đến

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1143 [độc quyền]
• chất nền [bắt đầuIdx, chiều dài]. trả về chuỗi con từ

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1142 của

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1145
• indexOf[searchStr, fromIdx?]. Trả về chỉ mục bắt đầu của lần xuất hiện đầu tiên của

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1146, bắt đầu từ một tùy chọn

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1147 [mặc định là 0];
• lastIndexOf[searchStr, fromIdx?]. Trả về chỉ mục bắt đầu của lần xuất hiện cuối cùng của

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1146

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  009, bắt đầu từ một tùy chọn

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1147 [mặc định là

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1152];
• lát cắt [bắt đầuIdx, endIdx]. Trả về chuỗi con từ

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1154 [bao gồm] đến

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1155 [không bao gồm]
• tách [dấu phân cách]. trả về một mảng bằng cách tách chuỗi bằng cách sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1156
• Tìm kiếm/Sửa đổi chuỗi bằng biểu thức chính quy. Xem "Biểu thức chính quy"

[ES6] Chuỗi mẫu nhiều dòng và thay thế

Trước ES6, Bạn có thể đặt một chuỗi ký tự bằng cách sử dụng dấu ngoặc đơn hoặc dấu ngoặc kép [e. g. ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

ES6 giới thiệu chuỗi mẫu, được phân tách bằng dấu ngoặc kép, ví dụ:

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Không cần thoát trích dẫn đơn hoặc kép bên trong chuỗi mẫu. Nhưng bạn cần sử dụng trình tự thoát cho trích dẫn ngược, tôi. e. ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Chuỗi mẫu hỗ trợ chuỗi nhiều dòng. Tất cả các khoảng trắng [trống, tab, dòng mới] trong dấu ngoặc kép là một phần của chuỗi nhiều dòng. Ví dụ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Hỗ trợ thay thế chuỗi mẫu, cho phép bạn nhúng bất kỳ biểu thức JavaScript hợp lệ nào như một phần của chuỗi ở dạng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Chuỗi mẫu nhiều dòng có thay thế cung cấp một cách thuận tiện hơn để viết ra đoạn HTML được định dạng. Ví dụ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

1168 Loại, Chữ & Hoạt động

Một biến kiểu

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Như đã đề cập, JavaScript thực hiện chuyển đổi kiểu tự động nếu cần thiết. Trong quá trình chuyển đổi loại, 6 giá trị sau được chuyển đổi thành

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

1. số

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   349
2. số

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   391 [Không phải là số],
3. chuỗi rỗng [

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   1113,

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   1178],
4. Giá trị

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   325,
5. boolean

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   042,
6. Đối tượng

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   036 [chưa phân bổ]

Tất cả các giá trị khác được chuyển đổi thành

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn cần ghi nhớ điều này.

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Các toán tử quan hệ sau, tạo ra kết quả

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Toán tử đẳng thức hoàn toàn

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

JavaScript cần cung cấp hai toán tử đẳng thức khác nhau, vì nó là kiểu lỏng lẻo và thực hiện chuyển đổi kiểu tự động trong nhiều tình huống. Ví dụ,

• Khi một số được so sánh với một chuỗi, chuỗi đó được chuyển đổi thành một số [hoặc

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  391 nếu nó không chứa một số hợp lệ]. Do đó,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1204 trả về

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  041. Nhưng,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1206 trả về

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  042, vì toán hạng không cùng kiểu

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1197,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1209,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1198,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1211 có thể được áp dụng cho boolean [và tất cả các loại JavaScript], e. g. ,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1212 cho

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  041 [vì chuỗi rỗng được chuyển thành

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  042];
• KHUYẾN NGHỊ sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1197 [hoặc

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1209], thay vì

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1198 [hoặc

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1211], trừ khi bạn chắc chắn rằng loại đó không quan trọng

Khi so sánh hai chuỗi, thứ tự mã hóa [bảng ASCII/Unicode] được sử dụng. Do đó, chuỗi

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Ví dụ,

Các toán tử boolean [hoặc logic] sau đây được cung cấp trong JavaScript

ghi chú.

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Đánh giá các hoạt động logic luôn bị ngắn mạch. Nghĩa là, hoạt động kết thúc ngay khi kết quả là chắc chắn, e. g. , [

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Chuyển đổi loại rõ ràng

Thời gian chạy JavaScript tự động thực hiện chuyển đổi loại. Tuy nhiên, đôi khi, bạn có thể cần chuyển đổi từ loại này sang loại khác một cách rõ ràng

Chuyển đổi một

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Chuyển đổi một

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Chuyển đổi số float thành số nguyên. Sử dụng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Kiểm soát luồng - Quyết định [Có điều kiện]

JavaScript cung cấp các cấu trúc điều khiển luồng này. Cú pháp giống như Java/C/C++

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Phép gán nullish logic

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Kiểm soát luồng - Vòng lặp [Lặp lại]

JavaScript cung cấp các cấu trúc vòng lặp sau. Cú pháp giống như Java/C/C++

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Các câu lệnh điều khiển vòng lặp sau được cung cấp [cùng cú pháp với Java/C/C++]

• ngắt - thoát khỏi vòng lặp trong cùng
• tiếp tục - hủy bỏ lần lặp hiện tại và tiếp tục với lần lặp tiếp theo
• nhãn mác. - cung cấp mã định danh cho câu lệnh, có thể được sử dụng bởi

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1266 và

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1267

Cố gắng tránh những tuyên bố này, vì chúng khó theo dõi và duy trì

Mảng

Một mảng là một bộ sưu tập được lập chỉ mục. Một mảng có thể được sử dụng để lưu trữ danh sách các mục [phần tử] dưới một tên duy nhất với chỉ số nguyên đang chạy. Bạn có thể tham chiếu phần tử riêng lẻ thông qua chỉ mục tích phân ở dạng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn có thể tạo một mảng bằng cách gán một ký tự mảng cho một biến, được gọi là Trình khởi tạo mảng, ở dạng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Hãy lưu ý rằng mảng chữ của JavaScript được đặt trong dấu ngoặc vuông

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn cũng có thể sử dụng Trình khởi tạo mảng để tạo một mảng có chỉ mục bị thiếu. Ví dụ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn có thể truy cập phần tử riêng lẻ của mảng thông qua chỉ mục tích phân, ở dạng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Độ dài của mảng được duy trì trong một biến có tên là

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Không giống như Java/C/C++, mảng JavaScript được cấp phát động. Bạn có thể thêm nhiều phần tử vào một mảng. Bạn cũng có thể xóa nội dung của một phần tử bằng từ khóa

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Mảng thường được xử lý chung bằng cách sử dụng một vòng lặp, e. g. ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

JavaScript cung cấp một vòng lặp

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Ví dụ,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

JavaScript cung cấp một vòng lặp

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Bạn có thể

• Sử dụng chỉ mục

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1289 để thêm một mục vào cuối mảng
• Sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1280 để xóa một chỉ mục cụ thể [đặt thành

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  325]
• Sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1292 để thêm một hoặc nhiều mục vào cuối mảng.

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1293 trả về độ dài kết quả của mảng
• Sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1294 để thêm một hoặc nhiều mục vào đầu mảng.

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1295 trả về độ dài kết quả của mảng
• Sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1296 để xóa và trả về phần tử cuối cùng của một mảng
• Sử dụng

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  1297 để xóa và trả về mục đầu tiên của một mảng

Ví dụ như,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Đối tượng

  
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• chiều dài. số lượng mặt hàng bao gồm

  
  
  
  
    
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  325 mặt hàng. Trên thực tế,

  
  
  
  
    
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  1278 được đặt thành chỉ số cuối cùng cộng với 1

Nó có những phương pháp thường được sử dụng

• mảng. tham gia [[dấu phân cách]]. nối các phần tử của một mảng lại với nhau thành một chuỗi duy nhất, được phân tách bằng ____11408 [mặc định là ____11409]. Ví dụ, ______1116
• str. split[[dấu phân cách, giới hạn]]. Đảo ngược của

  
  
  
  
    
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  1410. Lấy một chuỗi và chia thành một mảng dựa trên

  
  
  
  
    
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  1411. Ví dụ,
• mảng. concat[giá trị1, giá trị2,. , giá trịN]. trả về một mảng mới bao gồm mảng này và các mảng hoặc giá trị đã cho. Ví dụ, ______1117
• mảng. đảo ngược[]. đảo ngược thứ tự các phần tử trong mảng, phần tử đầu tiên trở thành phần tử cuối cùng. Ví dụ, ______1118
• mảng. loại[]. sắp xếp các phần tử trong mảng. Ví dụ, Take note take, theo mặc định, số cũng được sắp xếp dựa trên thứ tự ASCII/Unicode. Để sắp xếp các số theo số, bạn có thể cung cấp chức năng so sánh gọi lại. Hàm sẽ nhận 2 đối số, chẳng hạn như

  
  
  
  
    
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  1412 và

  
  
  
  
    
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  1413, đồng thời trả về một số âm nếu

  
  
  
  
    
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  1414;
• mảng. lát cắt [bắt đầuIdx, endIdx]. trích xuất và trả về một phần của mảng từ

  
  
  
  
    
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  1154 [bao gồm] đến

  
  
  
  
    
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  1155 [độc quyền]. Ví dụ, ______1119
• mảng. mối nối [startIdx, CountToRemove, insertItem1, insertItem2,. ]. loại bỏ các phần tử khỏi một mảng và chèn các phần tử vào vị trí của nó. Ví dụ,
• mảng. indexOf[searchItem[, startIdx]] và mảng. lastIndexOf[searchItem[, startIdx]]. tìm kiếm chỉ mục của mục tiến hoặc lùi. Nó trả về -1 nếu không tìm thấy mục. Ví dụ,
• đẩy[]. thêm một hoặc nhiều phần tử vào cuối một mảng và trả về độ dài kết quả của mảng
• nhạc pop[]. loại bỏ và trả về phần tử cuối cùng từ một mảng
• sự thay đổi[]. loại bỏ và trả về phần tử đầu tiên từ một mảng
• bỏ dịch []. thêm một hoặc nhiều phần tử vào phía trước của một mảng và trả về độ dài kết quả của mảng

Mảng cũng hỗ trợ các phương thức lặp này lặp qua từng mục của mảng, để hỗ trợ lập trình chức năng của mẫu giảm bản đồ bộ lọc

• mảng. forEach[gọi lại]. nhận một hàm với một đối số lặp qua tất cả các mục trong mảng.

  
  
  
  
    
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  120LƯU Ý. Cú pháp này nhằm hỗ trợ lập trình chức năng của mẫu filter-map-reduce
• mảng. bản đồ [gọi lại]. trả về một mảng mới, chứa tất cả giá trị trả về từ việc thực thi

  
  
  
  
    
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  1419 trên mỗi mục. Ví dụ,
• bộ lọc [gọi lại]. trả về một mảng mới, chứa các mục mà

  
  
  
  
    
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  1419 đã trả về cho

  
  
  
  
    
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  041. Ví dụ,
• mảng. mọi [gọi lại]. trả lại

  
  
  
  
    
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  041 nếu

  
  
  
  
    
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  1419 trả lại

  
  
  
  
    
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  041 cho TẤT CẢ các mặt hàng
• mảng. một số [gọi lại]. trả về

  
  
  
  
    
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  041 nếu

  
  
  
  
    
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  1419 trả về

  
  
  
  
    
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  041 cho ít nhất một mục trong mảng

Để biết thông số kỹ thuật chi tiết và các ví dụ về một đối tượng tích hợp sẵn, hãy kiểm tra "Tham khảo JavaScript chính"

Mảng kết hợp của các cặp khóa-giá trị

Một mảng kết hợp là một mảng của cặp khóa-giá trị. Thay vì sử dụng các số 0, 1, 2,. làm khóa như trong mảng thông thường, bạn có thể sử dụng bất kỳ thứ gì làm khóa trong mảng kết hợp. Mảng kết hợp được sử dụng rộng rãi trong JavaScript và jQuery

JavaScript không hỗ trợ mảng kết hợp gốc [nó thực sự cũng không hỗ trợ mảng gốc]. In JavaScript, associative arrays [and arrays] are implemented as objects [to be elaborate later]

You can create an associative array via the Object Initializer. For example,

Take note that Array initializer uses square brackets

  
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Functions

Functions are useful

• when you have to use the same codes several times
• as the JavaScript event handler
• make your program easier to read and understood

A function accepts zero or more arguments from the caller, performs the operations defined in the body, and returns zero or a single result to the caller

Functions are objects in JavaScript [to be discussed later]

The syntax for user-defined function is

  
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Functions are declared using the keyword

  
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"Hello" alert Box appears after the page is loaded.
  
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"Hello" alert Box appears after the page is loaded.
  
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"Hello" alert Box appears after the page is loaded.
  
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For client-side JavaScript, functions are generally defined in the

  
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To invoke a function

  
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"Hello" alert Box appears after the page is loaded.
  
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Function has access to an additional built-in variable called

  
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In JavaScript, primitive arguments are passed by value. That is, a copy of the variable is made and passed into the function. On the other hand, objects [including array and associative array] are passed by references. That is, if you modify the content of an object inside the function, the "copy" outside the function is also affected

JavaScript lets you invoke a function omitting some trailing arguments. It sets the omitted arguments to the value

  
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You can use this feature to provide default value to function argument, for example,

In the above example, we allow caller to omit the trailing arguments [

  
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"Hello" alert Box appears after the page is loaded.
  
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The common idiom in practice today is to use the short-circuited OR expression [as in

  
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"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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ES6 greatly simplify the above by introducing default parameter value in the form of

  
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ES6 also introduces rest/spread operator [

  
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In JavaScript, you can define an anonymous function [without a function name] using the following syntax

  
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Anonymous function is often used in event handlers and others

In JavaScript, a variable can hold a primitive [number, string, boolean] or an object

In JavaScript, functions are first-class object. Do đó, một biến cũng có thể chứa một đối tượng hàm. Ví dụ,

As seen in the above example, there are two ways to define a function

1. Sử dụng câu lệnh khai báo hàm ở dạng.

   
   
   
   
     
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   126
2. Use a function expression by assigning an anonymous function to a variable.

   
   
   
   
     
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   127

Recall that a function takes zero or more arguments from the caller. In JavaScript, arguments can be a primitive or object. Since functions are first-class objects in JavaScript, a function may take another function as its argument

Ví dụ: hàm sau lấy một hàm và một mảng làm đối số của nó và áp dụng hàm cho mảng

In JavaScript, you can define a function inside a function. For example,

You can return a function from a function. For example,

Interacting with Users

Client-side JavaScript provides these built-in top-level functions for interacting with the user

• alert[str]. Pop-up a box to alert user for important information. The user will have to click "OK" to proceed. The

  
  
  
  
    
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  001 returns nothing [or

  
  
  
  
    
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  325]
• prompt[str, defaultValue]. Pop-up a box to prompt user for input, with an optional

  
  
  
  
    
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  1455. The

  
  
  
  
    
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  030 returns the user's input as a string. For example,
• confirm[str]. Pop-up a box and ask user to confirm some information. The user will have to click on "OK" or "Cancel" to proceed. The

  
  
  
  
    
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  031 which returns a boolean value. For example,
• document. write[str], document. writeln[str]. Write the specified string to the current document. The

  
  
  
  
    
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  072 [write-line] writes a newline after the string, while

  
  
  
  
    
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  500 does not. Take note that browsers ignores extra white spaces, including newlines, in an HTML document, and treat newline as a single blank character. You need to write a

  
  
  
  
    
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  075 or

  
  
  
  
    
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  074 tag to ask the browser to display a line break

The following top-level built-in functions are available to client-side as well as server-side [or standalone]

• console. log[value]. write to the system [or error] console, used mainly for debugging

Other Top-level Built-in Functions

JavaScript also pre-defines the following top-level global functions

• parseInt[str], parseFloat[str]. parses the given

  
  
  
  
    
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  016 and returns the numeric value or

  
  
  
  
    
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  391 [Not-A-Number]. The

  
  
  
  
    
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  1464 accepts an optional

  
  
  
  
    
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  1465 [or base]. For example,

  
  
  
  
    
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  128
• Number[object]. returns the number representation of the object. It works for

  
  
  
  
    
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  1466 object, as well as many objects such as

  
  
  
  
    
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  058
• isFinite[number]. returns

  
  
  
  
    
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  041 if

  
  
  
  
    
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  089 is not

  
  
  
  
    
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  391,

  
  
  
  
    
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  1471 or

  
  
  
  
    
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  1472
• isNaN[number]. returns

  
  
  
  
    
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  041 if number is

  
  
  
  
    
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  391. Useful for checking the output of

  
  
  
  
    
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  377 and

  
  
  
  
    
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  1128
• đánh giá [mã]. evaluate the given JavaScript codes, which could be an expression or a sequence of statements. For example. [TODO]
• encodeURI[], decodeURI[], encodeURIComponent[], decodeURIComponent[]. encode or decode name-value pairs for the HTTP request, by replacing special characters with

  
  
  
  
    
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  1477. For example. [TODO]

An Introduction to Events [for Client-side JavaScript]

Client-side JavaScript are often event-driven. That is, a function [called event handler] will be fired in response to a certain user's or browser's action that generates an event

The commonly-used events are

• 
  
  
  
    
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  1478. generated when the user clicks on an HTML element

• 
  
  
  
    
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  1479,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
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  1480. generated when the user positions the mouse pointer inside/away from the HTML element

• 
  
  
  
    
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  518,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  1482. generated after the browser loaded a document, and before the next document is loaded, respectively

The event handler, called

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

More about events in the later sections

Objects

Objects are Everywhere

JavaScript is object-oriented [OO], and objects are everywhere in JavaScript. Arrays are objects. Functions are also objects. Primitives like string and number are auto-box to objects in many operations. Hầu hết mọi thứ trong JavaScript đều có thể là một đối tượng, có thể ngoại trừ

  
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Điều quan trọng là phải hiểu các đối tượng để thành thạo JavaScript, vì chúng ở khắp mọi nơi và chúng được sử dụng rộng rãi trong các trình cắm thêm JavaScript như jQuery, AngularJS, React, v.v.

Tuy nhiên, JavaScript không hỗ trợ tất cả các tính năng OO, để giữ cho ngôn ngữ đơn giản

Thuộc tính và phương thức

Trong các ngôn ngữ lập trình hướng đối tượng thông thường [như Java/C++/C#], một đối tượng là một tập hợp các thuộc tính và phương thức dưới một tên chung

• Thuộc tính [hay còn gọi là biến, thuộc tính]. chứa các giá trị được liên kết với đối tượng
• Phương thức [còn gọi là phép toán, hàm]. chứa các hành động mà đối tượng có thể thực hiện

Ví dụ: một đối tượng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Không giống như các ngôn ngữ OO chính thức, JavaScript được thiết kế trên mô hình OO đơn giản. A JavaScript object is simply a collection of properties. A property is an association between a name [or key] and value [i. e. , cặp tên-giá trị hoặc cặp khóa-giá trị]. If the value is a function [recall that functions are first-class objects that can be assigned to a variable], the property is known as a method. In other words, JavaScript does not differentiate between properties and methods like conventional OO languages. A method is simply a property holding a function

Creating Objects via Object Initializer

You can create a new object by directly assign an object literal to a variable, known as Object Initializer. The syntax is as follows

  
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• A JavaScript object is a collection of properties. Each property is an association of a name [key] and value pair
• The name and value are separated by a colon

  
  
  
  
    
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  1498
• The name-value pairs are separated by commas

  
  
  
  
    
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  1409. No comma is needed after the last name-value pair
• The property name could be a string or a number. For string name which is NOT a valid identifier [an valid identifier begins with an alphabet, underscore or dollar sign; and does not containing special characters like blank or

  
  
  
  
    
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  2900], you need to enclose the name with single or double quotes. Otherwise, the quotes are optional. For example, Take note that if the property name's string is a proper identifier, you can omit the quotes. This is commonly practiced by the developers
• The property value could be a literal, a variable or an expression
• A property's value could take all JavaScript types, including primitives [string, number, boolean], object or function. The property is known as a method, if it holds a function. JavaScript does not differentiate between variables and methods like conventional OO languages [Java/C++/C#]. A method is simply a property holding a function
• Objects created via Object Initializer are instances of class

  
  
  
  
    
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  2901

Trailing commas [sometimes called "final commas"] can be useful when adding new elements, parameters, or properties to JavaScript code. If you want to add a new property, you can add a new line without modifying the previously last line if that line already uses a trailing comma. This makes version-control diffs cleaner and editing code might be less troublesome. JavaScript has allowed trailing commas in array literals since the beginning, and later added them to object literals [ES?], and more recently, to function parameters [ES?] and to named imports and named exports [ES?]

In JavaScript, you can access an object's properties via either

1. The dot [

   
   
   
   
     
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   2902] operator. In the form of

   
   
   
   
     
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   2903 or

   
   
   
   
     
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   2904, just like Java/C++
2. The index

   
   
   
   
     
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   2905 operator [or bracket notation]. In JavaScript, you can also use the index operator to access the object properties, in the form

   
   
   
   
     
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   2906, just like accessing an array item

  
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You can remove a property [including method] via "

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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You can use the

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

You can use the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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An object's property can hold primitives [number, string]. It can also hold an object

A JavaScript object's property can also hold a function [or method]. You can assign to an anonymous function or a named function as shown in the following example

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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Many developers do not enquote the string

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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The string

  
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You can access an object's property via either dot operator or index operator. Dot operator is commonly used as it is more concise and used in conventional OO languages. But index operator allows access to properties containing special characters and selection of properties using variables, which is not feasible with dot operator. For example,

There are three ways to iterate through all properties of an object

1. for. in. đi qua tất cả các thuộc tính có thể đếm được của một đối tượng và chuỗi nguyên mẫu của nó
2. Vật. keys[obj]. return an array of all enumerable property names
3. Object. getOwnPropertyNames[obj]. return an array of all property names

Ví dụ,

  
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Establishes the default object for a set of statements. The syntax is

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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As discussed earlier

• An undeclared variable has type of

  
  
  
  
    
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  325, and its value cannot be referenced
• A declared but uninitialized variable has type of

  
  
  
  
    
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  325, with a special literal value of

  
  
  
  
    
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  325 too. [

  
  
  
  
    
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  325 is both a type and a literal value. ]
• A unallocated object has a special literal value of

  
  
  
  
    
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  036. Take note that

  
  
  
  
    
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  036 is an object

In boolean expressions, both the

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Built-in JavaScript Objects

JavaScript provides many useful global objects, such as

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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I shall discuss some commonly used objects here. For detailed specification and examples about a built-in object, check "Core JavaScript References"

Creating an Object via Constructor and the

  
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062 Operator

All the built-in objects define a so-called constructor, which is a special method having the same name as the object, for creating new instances. To invoke the constructor, you need to use a special

  
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For example, the

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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As seen from the above examples, the

  
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The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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The following methods are available to all built-in JavaScript objects

• toString[]. trả về một chuỗi mô tả về đối tượng này
• valueOf[]. converts this object to a primitive value such as

  
  
  
  
    
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  089

The

  
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1405 Object and Associative Arrays

For an introduction to arrays, read the "Arrays" section

Nowadays, we usually create an array via Array Initializer in the form of

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Ví dụ,

For an introduction to arrays, read the "Associative Arrays" section

JavaScript does not really support associative array, but allow you to add properties to an object, using the associative array syntax and index operator. In other words,

In JavaScript, we usually create an associative array using a generic object [via the Object Initializer]. You can also create an associative array via

  
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In this case, additional properties are added into an

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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The

  
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1466 Object vs

  
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331 Primitive Type

JavaScript provides primitive

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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A string can be created in two ways

1. directly assigned a string literal in the form of

   
   
   
   
     
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   2988 or

   
   
   
   
     
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   2989 to a variable, resulted in a

   
   
   
   
     
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   331 primitive
2. invoke the

   
   
   
   
     
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   1466 object constructor to construct a

   
   
   
   
     
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   1466 object

Ví dụ như,

The former is a primitive

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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A

  
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"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

389 Object vs

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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089 Primitive Type

JavaScript provides primitive

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Đối tượng

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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10 so với loại boolean

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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11

JavaScript provides primitive

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

058 Object

Commonly-used constructors

• 
  
  
  
    
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  19. constructs a

  
  
  
  
    
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  058 object with the current date and time

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
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  21. xây dựng một đối tượng

  
  
  
  
    
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  058 với chuỗi ngày-giờ đã cho ở dạng có thể chấp nhận được [e. g. , "Month, day, year, hours. minutes. seconds"]

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  23. where month is 0-11 for Jan to Dec

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  24

Commonly-used methods

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  077,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  26,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  078,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  28,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  079,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  30. lấy/đặt ngày [1-31], tháng [0-11 từ tháng 1 đến tháng 12], năm [năm có 4 chữ số]

• 
  
  
  
    
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  080. get the day of the week [0-6 for Sunday to Saturday]

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  066,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  33,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  34,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  35,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  36,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  37. get/set the hours/minutes/seconds

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  38,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  39. get/set the number of milliseconds since January 1, 1970, 00. 00. 00

The

  
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40 Object

Commonly-used properties

• 
  
  
  
    
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  41,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  42. Euler’s constant and

  
  
  
  
    
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  42

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  44,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  45,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  46,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  47.

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  48,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  49,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  50,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  51

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  52,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  53. căn bậc hai của 2 rưỡi

Commonly-used methods

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  54

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  55,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  56,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  57,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  58,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  59,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  60,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  61

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  62,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  63,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  64

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  65,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  66,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  67,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  68

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  69,

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  70

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  71. returns a pseudo-random number between 0 and 1

The

  
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72 Object

For an introduction to functions, read "Function" section

Every function in JavaScript is actually a

  
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A variable can be assigned a

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Ví dụ,

If a function is called only once, you can use an anonymous function, omitting the function name. Anonymous functions are commonly-used as event handler, e. g. ,

You can define a inline [anonymous] function and assign it to a variable as follows

Besides using

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Cú pháp cho hàm tạo

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

More on Objects

Prototype-based vs. dựa trên lớp

OO của JavaScript dựa trên nguyên mẫu, thay vì dựa trên lớp như Java/C++/C#

Ngôn ngữ OO dựa trên lớp [chẳng hạn như Java/C++/C#] được thành lập dựa trên các khái niệm về lớp và thể hiện. Một lớp là một bản in màu xanh hoặc khuôn mẫu của những thứ cùng loại. Một thể hiện là một hiện thực cụ thể của một lớp. Ví dụ: "

  
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On the other hand, a prototype-based OO language [such as JavaScript] simply has objects [or instances]. A new object can be constructed based on an existing object as prototype. There is no class definition, and hence, they are also called class-less OO languages

In JavaScript

• Every JavaScript object has a prototype. Nguyên mẫu cũng là một đối tượng. Một đối tượng JavaScript được tạo từ một đối tượng nguyên mẫu và nhận các thuộc tính ban đầu của nó từ nguyên mẫu
• Every JavaScript object has an internal property called

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  89, which holds its prototype object. Khi bạn xác định một đối tượng mới thông qua "Trình khởi tạo đối tượng" [hoặc hàm tạo

  
  
  
  
    
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  90], thì

  
  
  
  
    
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  89 của nó được đặt thành một đối tượng tích hợp có tên là

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  92. Nói cách khác, đối tượng mới sử dụng

  
  
  
  
    
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  92 làm nguyên mẫu và nhận các thuộc tính ban đầu của nó từ

  
  
  
  
    
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  92. The

  
  
  
  
    
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  89 property is not enumerable, i. e, nó sẽ không hiển thị trong vòng lặp

  
  
  
  
    
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  96.
  For example,
• Any object can be the prototype of new objects. For example,

  
  
  
  
    
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  2901 is the prototype of

  
  
  
  
    
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  98;

  
  
  
  
    
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  98 is the prototype for

  
  
  
  
    
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  85;

  
  
  
  
    
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  85 is the prototype for

  
  
  
  
    
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  002. These objects form a so-called prototype chain, i. e. ,

  
  
  
  
    
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  003. Take note that

  
  
  
  
    
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  2901 is always on top of the prototype chain for every JavaScript object
• You can add or remove properties for an object at runtime, which is not permitted in conventional OO languages

Defining Your Own Custom Objects via a Constructor

In JavaScript, you can create your own custom objects by defining a constructor. A constructor is simply a function, which can be invoked via the

  
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Theo quy ước, tên hàm tạo bắt đầu bằng một chữ cái viết hoa

  
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"

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Let us define a constructor for our custom

  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

1. Properties [including methods] are declared inside the constructor via

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   014, which can then be initialized
2. Methods can be declared inside the constructor via

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   015. There are a few ways to provide the method's definition
   1. Define an ordinary

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      503, and assign the

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      017 [without parentheses, which is a

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      503 type] to

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      015, as in the

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      013
   2. Assign

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      015 to an inline function, as in the

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      012
   3. Invoke the

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      72 constructor with

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      062 operator [rarely-used].

      
      
      
      
        
        JavaScript Example: Events onload, onmouseover and onmouseout
        
      
      
        
      "Hello" alert Box appears after the page is loaded.
        
      Point your mouse pointer here!!!
      
      

      145
3. To invoke a method, use

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   025
4. The

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   2970 is a special method, which returns a string description of this object. The

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   2970 will be implicitly invoked if an object is passed into the

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   002,

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   071 or

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   023 operator [like Java]

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

89 and

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

032

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

In JavaScript, the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

1. Create a new generic object using built-in root

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   2901 as prototype
2. Assign this newly created object to

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   524 variable
3. Run the constructor function, which typically adds properties to

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   524
4. Đặt thuộc tính bên trong

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   89 thành

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   039 [trong ví dụ trên,

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   040]. The

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   89 property is not enumerable [i. e, nó sẽ không hiển thị trong vòng lặp

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   96]. Nó được sử dụng để duy trì cái gọi là "chuỗi nguyên mẫu" của các đối tượng
5. Return the newly created object

Take note that you can invoke the constructor function WITHOUT the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Try tracing the object created in the above example via Chrome's Developer Tools, which could display the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

All the JavaScript constructor function objects [in fact, all function objects] have a special property called

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

In the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The constructor's

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

When you reference a property, JavaScript first checks if the property exists locally [or own property]; otherwise, it checks the prototype chain through the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

In practice, we defines methods [and static variables] in

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Objects in JavaScipt form prototype chains. In the above example, a prototype chain is

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

When you reference an object property, JavaScript follow these steps to locate the property

1. Check if the property exists locally [i. e. , tài sản riêng]
2. Otherwise, check the

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   89 property. This continues recursively up the prototype chain. The process is called "lookup in the prototype chain"

Hence, in the above example, all the properties in

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Every object has a

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

[LÀM]

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Inheritance via Prototype Chain

You can implement inheritance in JavaScript via the prototype chain. For example,

[LÀM]

Getter and Setter

In languages like Java, you can declare a variable to be

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Moreover, in JavaScript, you can define getter/setter as properties instead of methods in one of the following two ways

1. via built-in functions

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   091 or

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   092;
2. inside the "object initializer" via keywords

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   093 and

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   094

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Notes

1. The

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   097 allows you to define multiple properties; while

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   098 for a single property
2. You invoke the getters/setters like properties with assignment operator, instead of via function call

Notes

1. The getter/setter are defined inside Object Initializer via keywords

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   093 and

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   094 with a rather strange syntax, as shown in the example

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

2901's Properties

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

All JavaScript objects inherited a special property called

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

[TODO] more Object's properties

API mô hình đối tượng tài liệu [DOM] cho JavaScript

Document Object Model [DOM], is a standard API that allows programmers to access and manipulate the contents of an HTML/XHTML/XML document dynamically inside their program. It models an HTML/XHTML/XML document as an object-oriented, tree-like structure, known as a DOM-tree, consisting of nodes resembling the tags [elements] and contents. DOM also provides an interface for event handling, allowing you to respond to user's or browser's action

DOM API is implemented in many languages such as Java, JavaScript, Perl, and ActiveX. DOM API specification is maintained by W3C. DOM has various levels

• DOM Level 0 [DOM0] [Pre-W3C]. obsolete
• DOM Level 1 [DOM1] [W3C Oct 1998]. obsolete
• DOM Level 2 [DOM2] [W3C Nov 2000] and DOM Level 2 HTML [HTML DOM2] [W3C Jan 2003]
• DOM Level 3 [DOM3] [W3C Apr 2004]. yet to be fully supported by browsers

jQuery is much better in selecting and manipulating DOM element. You should use jQuery in production. I keep these sections here for completeness

Finding and Selecting Elements

In JavaScript, we often use DOM API to select elements within the current document, so as to access or manipulate their contents. Các chức năng được sử dụng phổ biến nhất là

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

You can use wildcard

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

The above functions select element[s] based on the unique

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Beside the above selection functions, there are many other selection functions available. However, I strongly recommend that you stick to the above functions. I listed below the other function below for completeness

1. 
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0020 returns an array of all

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0021 elements, same as

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0022

2. 
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0023. return an array of allelements

3. 
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0024 and

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   0025. return all the hyperlinks

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   009and anchors

   
   
   
   
     
     JavaScript Example: Events onload, onmouseover and onmouseout
     
   
   
     
   "Hello" alert Box appears after the page is loaded.
     
   Point your mouse pointer here!!!
   
   

   009elements. [To confirm. ]

Manipulating Element's Content through the

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

537 Property

You can access and modify the content of an element via the "

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Ví dụ,

"

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

DOM Tree & Nodes

W3C recommends that you access and manipulate HTML elements via the DOM tree and nodes. However, it is really an overkill for writing simple JavaScripts. I present them here again for completeness

When a browser loads an HTML page, it builds DOM models a web page in a hierarchical tree-like structure composing of nodes, resembling its HTML structure

An example of an HTML document with the corresponding DOM-tree is given follow. Take note that the text content of an element is stored in a separate Text node

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Load the web page onto Firefox, and use the firebug to inspect the DOM tree.

A DOM-tree comprises the following types of nodes

1. Document Node. the root node representing the entire HMTL document
2. Element node. represents an HTML element [or tag]. An element node may have child nodes, which can be either element or text node. Element node may also have attributes
3. Text Node. contains the text content of an element
4. Others. such as comment, attribute

A DOM node has these properties

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  0031. contain the name of the node, which is read-only. The

  
  
  
  
    
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  0031 for an Element node is the tag-name;

  
  
  
  
    
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  0031 for the Document node is

  
  
  
  
    
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  0034;

  
  
  
  
    
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  0031 for Text nodes is

  
  
  
  
    
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  0036

• 
  
  
  
    
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  0037. contain the value of the node.

  
  
  
  
    
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  0037 cho nút Văn bản là văn bản được chứa;

• 
  
  
  
    
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  0040. một số nguyên cho biết loại nút, e. g. , Element [1], Attribute [2], Text [3], Comment [8], Document [9]

• 
  
  
  
    
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  0041. tham chiếu đến nút cha. Chỉ có một nút cha trong cấu trúc cây

• 
  
  
  
    
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  0042. array [or node-list] of child nodes

• 
  
  
  
    
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  0043,

  
  
  
  
    
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  0044. reference to the first and last child node

• 
  
  
  
    
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  0045,

  
  
  
  
    
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  0046. reference to the previous and next sibling in the same level

Take note of the difference between singular and plural terms. For example,

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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The root node of the DOM tree is called

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

For example, you can use the following node property to access the Text node

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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The following JavaScript lists all the nodes in the section, in a depth-first search manner, via a recursive function

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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Accessing the HTML element via Node interface may not be too useful nor practical for JavaScript applications, as you need to know the actual topological structure of the DOM-tree. Furthermore, some browsers [e. g. , firefox] may create extra Text nodes to contain the white spaces between tags

Text Node

DOM models the texts enclosed by HTML tags as a separate text node. It cannot have child node. To retrieve the text content, you could the property

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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Attribute Properties

To access an attribute of an Element node called

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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• property

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  0056, where

  
  
  
  
    
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  0057 is the name of the attribute, or
• methods

  
  
  
  
    
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  0058 and

  
  
  
  
    
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  0059

Ví dụ,

Attribute

  
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0060 [for CSS]

Element has a property called style, which models CSS style with CSS properties such as

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

Manipulating Nodes

A Node object has these functions

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
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  0063. returns

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  041 if this node has at least one child node
• Manipulating child node

  • 
    
    
    
      
      JavaScript Example: Events onload, onmouseover and onmouseout
      
    
    
      
    "Hello" alert Box appears after the page is loaded.
      
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    0065. insert a node before an existing child node

  • 
    
    
    
      
      JavaScript Example: Events onload, onmouseover and onmouseout
      
    
    
      
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    0066. replace an existing child node

  • 
    
    
    
      
      JavaScript Example: Events onload, onmouseover and onmouseout
      
    
    
      
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    0067. remove the specified child node

  • 
    
    
    
      
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    "Hello" alert Box appears after the page is loaded.
      
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    0068. append the given node as the last child

• 
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
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  0069

  
  
  
  
    
    JavaScript Example: Events onload, onmouseover and onmouseout
    
  
  
    
  "Hello" alert Box appears after the page is loaded.
    
  Point your mouse pointer here!!!
  
  

  0070

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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To create new text node, you can use

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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Similarly, you can use

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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For example, we shall create a new text node, as a child of a new

element. We shall then append the new

element as the last child of

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
Point your mouse pointer here!!!

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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Change the last line to

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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You can remove a child node from a parent node via

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
"Hello" alert Box appears after the page is loaded.
  
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For example, let remove the last

from

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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The

  
  JavaScript Example: Events onload, onmouseover and onmouseout
  


  
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019 object

The

  
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What does the below statement evaluate to in JavaScript 4 3 2 1?

Which of the following is the correct way for calling the JavaScript code 1 point a preprocessor B triggering event C RMI D function method?

What is the correct JavaScript syntax to change the content of the following HTML code?

Which type of JavaScript language is?