How to uppercase an array in javascript

To recap :

There are 2 main methods to do it :

1. Using the modern Javascript ES6 version with arrow function and map[] iterator :

// the test array

const items = ['item1', 'item2', 'item3', 'item4', 'item5', 'item6'];

// declare the function with arrow function using the map iterator and the 
// toUpperCase[] buildin method

const countItems = arr => arr.map[item => item.toUpperCase[]];

2. Using the old good function style with a simple for loop, the toUpperCase[] buildin method and the push[] method

// the test array

const items = ['item1', 'item2', 'item3', 'item4', 'item5', 'item6'];

// the old way

function countItems[arr] {
  newarray = [];
  for [let i = 0; i < arr.length; i++] {
    
    newarray.push[arr[i].toUpperCase[]];
  }
  return newarray;
};

3. call the function with any of the above snippets

console.log[countItems[items]];

// Should print

[ 'ITEM1', 'ITEM2', 'ITEM3', 'ITEM4', 'ITEM5', 'ITEM6' ]

hope that this answer adds a small stone to whatever you want to build

In JavaScript, you can use the Array.map[] method to iterate over all elements and then use the string methods to change the case of the elements.

Here is an example that demonstrates how to use the String.toUpperCase[] method along with Array.map[] to uppercase all elements in an array:

const names = ['Ali', 'Atta', 'Alex', 'John'];

const uppercased = names.map[name => name.toUpperCase[]];

console.log[uppercased];

// ['ALI', 'ATTA', 'ALEX', 'JOHN']

The toUpperCase[] method converts a string to uppercase letters without changing the original string.

To convert all elements in an array to lowercase, you can use another JavaScript method called String.toLowerCase[] as shown below:

const names = ['Ali', 'Atta', 'Alex', 'John'];

const lowercased = names.map[name => name.toLowerCase[]];

console.log[lowercased];

// ['ali', 'atta', 'alex', 'john']

Both string methods work in all modern browsers, and IE6 and above. However, the Array.map[] was introduced in ES6 and only supports IE9 and up. On the other hand, arrow functions do not work in IE at all.

To support legacy browsers [IE9 and above], you should use the normal function instead:

const uppercased = names.map[function [name] {
    return name.toUpperCase[];
}];

const lowercased = names.map[function [name] {
    return name.toLowerCase[];
}];

To learn more about JavaScript arrays and how to use them to store multiple pieces of information in one single variable, take a look at this guide.

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let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = names.map[name => name.toLowerCase[]];

console.log[convertedNames];
// Output: ["john", "william", "elijah", "michael"]

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = names.map[name => name.toUpperCase[]];

console.log[convertedNames];
// Output: ["JOHN", "WILLIAM", "ELIJAH", "MICHAEL"]

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = [];
for [let i = 0; i < names.length; i++] {
  convertedNames[i] = names[i].toLowerCase[];
}

console.log[convertedNames];
// Output: ["john", "william", "elijah", "michael"]

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = [];
for [let i = 0; i < names.length; i++] {
  convertedNames[i] = names[i].toUpperCase[];
}

console.log[convertedNames];
// Output: ["JOHN", "WILLIAM", "ELIJAH", "MICHAEL"]

let convertedNames = names.join['$$'].toLowerCase[].split['$$'];

let convertedNames = names.join['$$'].toUpperCase[].split['$$'];

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