Hướng dẫn dùng w3schoolsjava JavaScript

JavaScript is the world's most popular programming language.

JavaScript is the programming language of the Web.

JavaScript is easy to learn.

This tutorial will teach you JavaScript from basic to advanced.

Start learning JavaScript now »

Examples in Each Chapter

With our "Try it Yourself" editor, you can edit the source code and view the result.

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Use the Menu

We recommend reading this tutorial, in the sequence listed in the menu.

If you have a large screen, the menu will always be present on the left.

If you have a small screen, open the menu by clicking the top menu sign ☰.

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Learn by Examples

Examples are better than 1000 words. Examples are often easier to understand than text explanations.

This tutorial supplements all explanations with clarifying "Try it Yourself" examples.

If you try all the examples, you will learn a lot about JavaScript, in a very short time!

JavaScript Examples »

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Why Study JavaScript?

JavaScript is one of the 3 languages all web developers must learn:

   1. HTML to define the content of web pages

   2. CSS to specify the layout of web pages

   3. JavaScript to program the behavior of web pages

This tutorial covers every version of JavaScript:

• The Original JavaScript ES1 ES2 ES3 (1997-1999)
• The First Main Revision ES5 (2009)
• The Second Revision ES6 (2015)
• The Yearly Additions (2016, 2017, 2018)

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Learning Speed

In this tutorial, the learning speed is your choice.

Everything is up to you.

If you are struggling, take a break, or re-read the material.

Always make sure you understand all the "Try-it-Yourself" examples.

The only way to become a clever programmer is to: Practice. Practice. Practice. Code. Code. Code !

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Commonly Asked Questions

• How do I get JavaScript?
• Where can I download JavaScript?
• Is JavaScript Free?

You don't have to get or download JavaScript.

JavaScript is already running in your browser on your computer, on your tablet, and on your smart-phone.

JavaScript is free to use for everyone.

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My Learning

Track your progress with the free "My Learning" program here at W3Schools.

Log into your account, and start earning points!

This is an optional feature, you can study W3Schools without using My Learning.

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JavaScript References

W3Schools maintains a complete JavaScript reference, including all HTML and browser objects.

The reference contains examples for all properties, methods and events, and is continuously updated according to the latest web standards.

Complete JavaScript Reference »

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JavaScript Quiz Test

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This page contains some examples of what JavaScript can do.

JavaScript Can Change HTML Content

One of many JavaScript HTML methods is getElementById().

The example below "finds" an HTML element (with id="demo"), and changes the element content (innerHTML) to "Hello JavaScript":

Example

document.getElementById("demo").innerHTML = "Hello JavaScript";

Try it Yourself »

JavaScript accepts both double and single quotes:

Example

document.getElementById('demo').innerHTML = 'Hello JavaScript';

Try it Yourself »

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JavaScript Can Change HTML Attribute Values

In this example JavaScript changes the value of the src (source) attribute of an tag:

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JavaScript Can Change HTML Styles (CSS)

Changing the style of an HTML element, is a variant of changing an HTML attribute:

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JavaScript Can Hide HTML Elements

Hiding HTML elements can be done by changing the display style:

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JavaScript Can Show HTML Elements

Showing hidden HTML elements can also be done by changing the display style:

Did You Know?

JavaScript and Java are completely different languages, both in concept and design.

JavaScript was invented by Brendan Eich in 1995, and became an ECMA standard in 1997.

ECMA-262 is the official name of the standard. ECMAScript is the official name of the language.

JavaScript Versions »