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How to create and use an Array ?

William Quesnot's photo
William Quesnot
·Jan 16, 2022·

2 min read

Array are like lists, you can list and modify the array. The length of an array may vary. There are many ways to create an Array in Javascript.

let arr = new Array(); // An array has been created by 'new Array'

let arr = []; // An array has been created by [ ]

But it is not necessary to use the first method, Create an Array like this : put the string under quotes,

let colors = ['Green']; 

console.log(colors);
// Green

console.log(colors.length)
// 1

Don’t forget to verify if everything is ok, with console.log() Access (via index) an array element

// Red

Add an element at the start of your table :

let newColors = colors.unshift('Red');

// ['Red','Green'];

Add an element at the end of your array :

let newColors = colors.push('Blue');
// ['Red','Green','Blue'];

Find an element in your array by his index :

let posGreen = colors.indexOf('Green');

console.log(posGreen);
// 1

Then remove it by his index :

let removedGreen = colors.splice(posGreen, 1); 
// Delete an element from posGreen;

console.log(colors);
// ['Red', 'Blue'];

Delete the first element of your array :

let firstElement = colors.shift();
// 'Red' has been deleted

console.log(colors);
/ ['Green','Blue'];

Delete the last element of your array :

let lastElement = colors.pop(); 
// 'Blue' has been deleted

console.log(colors);
// Green

Copy an array :

let copyArray = colors.slice();

console.log(copyArray);
// Green

How to acceed to an element of an array :

let array = ['Green','Blue','Red','Black','Yellow','Brown','White'];

console.log(array[0]);// Show the first element of the array
// Green 
console.log(array[1]); // Show the second element of the array 
// Blue
console.log(array[4]); // Show the 5th element of the array
// Yellow
console.log(array[array.length - 1]); // Show the last element of the array