JavaScript- Arrays are Equal or Not

Last Updated : 09 Jan, 2025

These are the following approaches to compare two arrays in JavaScript:

1. Using the JSON.stringify() Method

JavaScript provides a function JSON.stringify() method in order to convert an object whether or array into a JSON string. By converting it into JSON strings, we can directly check if the strings are equal or not.

JavaScript

let a1 = [1, 2, 3, 5];
let a2 = [1, 2, 3, 5];

if (JSON.stringify(a1) == JSON.stringify(a2))
    console.log("True");
else
    console.log("False");

Output

True
False

2. Using JavaScript for Loop

In this method, we will compare each element of the array one by one using for loop. we manually check each and every item and return true if they are equal otherwise return false.

JavaScript

let a = [1, 2, 3, 5];
let b = [1, 2, 3, 5];

// If length is not equal
if (a.length != b.length)
    console.log(false);
else {

    // Comparing each element of array
    for (let i = 0; i < a.length; i++)
        if (a[i] != b[i])
            return console.log(false);
    ;
    return console.log(true);
}

Output

True

3. String Comparison

While JavaScript does not have an inbuilt method to directly compare two arrays, it does have inbuilt methods to compare two strings. Strings can also be compared using the equality operator. Therefore, we can convert the arrays to strings, using the Array join() method, and then check if the strings are equal.

JavaScript

let a = [1, 2, 3, 5];
let b = [1, 2, 3, 5];
let res = a.join() == b.join();
console.log(res);

Output

true

4. Using Array every() Method

The Javascript Array.every() method considers all the elements of an array and then further checks whether all the elements of the array satisfy the given condition (passed by in user) or not that is provided by a method passed to it as the argument.

JavaScript

const compareFunc = (a, b) =>
    a.length === b.length &&
    a.every((element, index) => element === b[index]);

let a = [1, 2, 3, 5];
let b = [1, 2, 3, 5];
console.log(compareFunc(a, b));

Output

true

5. Using Lodash _.isEqual() Method

In this approach, we are using the Lodash _.isEqual() method that return boolean value of the result whether that given arrays are equal or not.

JavaScript

// Defining Lodash variable 
const _ = require('lodash');

let a1 = [1, 2, 3, 4]

let a2 = [1, 2, 3, 4]

// Checking for Equal Value 
console.log("The Values are Equal : "
    + _.isEqual(a1, a2));

Output:

The Values are Equal : true

6. Using Set

The Set object in JavaScript allows you to store unique values of any type, including arrays. By converting arrays to sets, you can easily compare them, as sets automatically remove duplicate values.

JavaScript

function compareArrays(a1, a2) {
    const s1 = new Set(a1);
    const s2 = new Set(a2);

    if (s1.size !== s2.size) {
        return false;
    }

    for (const item of s1) {
        if (!s2.has(item)) {
            return false;
        }
    }

    return true;
}

const a1 = [1, 2, 3, 4];
const a2 = [4, 3, 2, 7];

console.log(compareArrays(a1, a2));

Output

true

7. Using reduce and some Methods

This method involves reducing the arrays into an object that keeps track of the elements and their counts, then comparing these objects.

JavaScript

function arraysEqual(a1, a2) {
    if (a1.length !== a2.length) return false;

    let countElements = (arr) =>
        arr.reduce((acc, val) => {
            acc[val] = (acc[val] || 0) + 1;
            return acc;
        }, {});

    let c1 = countElements(a1);
    let c2 = countElements(a2);

    return !Object.keys(c1).some(key => c1[key] !== c2[key]);
}

let a1 = [1, 2, 3, 4];
let a2 = [4, 3, 2, 1];
let a3 = [1, 2, 3, 5];

console.log(arraysEqual(a1, a2));
console.log(arraysEqual(a1, a3));

Output

true
false

8. Using Array.prototype.sort() Method

This approach leverages the fact that two arrays are equal if they contain the same elements in the same order. By sorting both arrays and then comparing them element by element, we can determine if they are equal. This method is particularly useful for comparing arrays where the order of elements does not matter.

JavaScript

function arraysEqual(a1, a2) {
    if (a1.length !== a2.length) return false;

    let s1 = a1.slice().sort();
    let s2 = a2.slice().sort();

    for (let i = 0; i < s1.length; i++) {
        if (s1[i] !== s2[i]) return false;
    }
    return true;
}
let a1 = [3, 1, 2];
let a2 = [2, 3, 1];

console.log(arraysEqual(a1, a2));

Output

true

JavaScript is best known for web page development but it is also used in a variety of non-browser environments. You can learn JavaScript from the ground up by following this JavaScript Tutorial and JavaScript Examples.

How to call function from it name stored in a string using JavaScript ?

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Article Tags :

JavaScript- Arrays are Equal or Not

1. Using the JSON.stringify() Method

2. Using JavaScript for Loop

3. String Comparison

4. Using Array every() Method

5. Using Lodash _.isEqual() Method

6. Using Set

7. Using reduce and some Methods

8. Using Array.prototype.sort() Method

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