An Overview of Array Methods in JavaScript

Learn about how to manipulate arrays in JavaScript

Let’s create an array:

var numbers = [1,2,3,4,5]

Array elements are accessed using an index. The index starts from 0 . So if we want to access the first element, then we need to access using index 0.

numbers[0] // 1

numbers[3] // 4

numbers[9] // undefined

Find the length of the array

numbers.length

Get the last element of the array

let len = numbers.length;

let index = len - 1;

let lastElement = numbers[index]

Adding an element to the end of an array

numbers.push(6);

numbers; // [1,2,3,4,5,6]

Adding element to the beginning of an array

numbers.unshift(0);

numbers; // [0,1,2,3,4,5,6]

Deleting the last element of an array

numbers.pop()

Delete the first element of the array

numbers.shift()

Delete an element at specific index

let numbers = [1,2,3,4,5];

let index = 2;

numbers.splice(index,1);

numbers; [1,2,4,5]

Adding an element at a specific index

let numbers = [1,2,5];

let index = 2;

let elements = [3,4]

numbers.splice(index,0, ...elements);

numbers; [1, 2, 3, 4, 5]

Updating elements

var numbers = [1,2,2,4,5]

numbers[2] = 3;

numbers; // [1,2,3,4,5]

Find if an element is present in an array

var numbers = [1,2,3,4,5]

numbers.includes(1);// true

numbers.includes(10);// false

Find the index of the element

var numbers = [1,2,3,4,5]

numbers.indexOf(1); // 0

numbers.indexOf(10); // -1(if element not present )

Iterating over an array

var numbers = [1,2,3,4,5]

for(let i = 0; i < numbers.length; i++) {
    console.log(numbers[i]);
}

// example 1

numbers.forEach(elem => console.log(elem));

Reverse an array

var numbers = [1,2,3,4,5]

numbers.reverse(); // [5, 4, 3, 2, 1]

Filter array elements

var numbers = [1,2,3,4,5];

numbers.filter((elem) => elem > 3);// [4,5]

Mapping all elements with function and create a new array

var numbers = [1,2,3,4,5]; 

var doubledNum =  numbers.map(item => item *2 );

doubledNum; // [2,4,6,8,10]

Sorting an array

let num= [1, 2, 3, 4, 5, 6];

// sort in descending order
let descOrder = num.sort( (a, b) => a > b ? -1 : 1 );

console.log(descOrder); // output: [6, 5, 4, 3, 2, 1]

// sort in ascending order
let ascOrder = num.sort((a, b) => a > b ? 1 : -1);

console.log(ascOrder); // output: [1,2,3,4,5,6]

Create a string from Array

var test = ["This", "is", "a", "test."]

test.join(" "); // "This is a test."

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