How to create an array containing non-repeating elements in JavaScript ?

Last Updated : 03 Jul, 2024

In this article, we will learn how to create an array containing non-repeating elements in JavaScript.

The following are the two approaches to generate an array containing n number of non-repeating random numbers.

Table of Content

Using do-while loop and includes() Method
Using a set and checking its size
Using forEach and includes method

Method 1: Using do-while loop and includes() Method

Here, the includes() function checks if an element is present in the array or not.

Example:

// You can take this value from user
const n = 5

// Initial empty array
const arr = [];

// Null check
if (n == 0) {
    console.log(null)
}

do {
    // Generating random number
    const randomNumber = Math
        .floor(Math.random() * 100) + 1

    // Pushing into the array only 
    // if the array does not contain it
    if (!arr.includes(randomNumber)) {
        arr.push(randomNumber);
    }
} 
while (arr.length < n);

// Printing the array elements
console.log(arr)

 
// You can take this value from user
const n = 5​// Initial empty arrayconst arr = [];​// Null checkif (n == 0) {    console.log(null)}​do {    // Generating random number    const randomNumber = Math        .floor(Math.random() * 100) + 1​    // Pushing into the array only     // if the array does not contain it    if (!arr.includes(randomNumber)) {        arr.push(randomNumber);    }} while (arr.length < n);​// Printing the array elementsconsole.log(arr)

Output

[ 29, 36, 38, 83, 50 ]

Method 2: Using a set and checking its size

Remember that a set does not allow duplicate elements.

Example:

// You can take this value from user
const n = 5

// Initial empty array
const arr = [];

// Null Check
if (n == 0) {
    console.log(null)
}

let randomnumbers = new Set, ans;

// We keep adding elements till
// size of set is equal to n 
while (randomnumbers.size < n) {

    // Generating random number 
    // and adding it
    randomnumbers.add(Math.floor(
        Math.random() * 100) + 1);
}

// Copying set elements into 
// the result array
ans = [...randomnumbers];

// Printing the array
console.log(ans)

 
// You can take this value from user
const n = 5​// Initial empty arrayconst arr = [];​// Null Checkif (n == 0) {    console.log(null)}​let randomnumbers = new Set, ans;​// We keep adding elements till// size of set is equal to n while (randomnumbers.size < n) {​    // Generating random number     // and adding it    randomnumbers.add(Math.floor(        Math.random() * 100) + 1);}​// Copying set elements into // the result arrayans = [...randomnumbers];​// Printing the arrayconsole.log(ans)

Output

[ 41, 75, 57, 62, 92 ]

Method 3: Using forEach and includes method

Using forEach and includes to remove duplicates involves iterating over the array and adding each item to a new array only if it isn't already included. This ensures all elements in the result are unique.

Example: The removeDuplicates function iterates through an array (`arr`), checking each element. If an element isn't already in nonRepeatingArray, it adds it. This ensures `nonRepeatingArray` contains only unique elements.