JavaScript - check if arrays are identical

In this article, we would like to show you how to check if arrays are identical in JavaScript.

Practical example

To check if arrays are identical we take the following steps:

1. Check if the length of both arrays is the same (if it's not they are different),
2. iteratively check each element to find out if they are equal.

// ONLINE-RUNNER:browser;

function areEqual(array1, array2) {
    if (array1 === array2) {
        return true;
    }
    if (array1.length !== array2.length) {
        return false;
    }
    for (var i = 0; i < array1.length; ++i) {
        if (array1[i] !== array2[i]) return false;
    }
    return true;
}


// Usage example

console.log(areEqual([1, 2, 3], [1, 2, 3])); // true
console.log(areEqual([1, 2, 3], [3, 2, 1])); // false

ES6 version

In this section, we've used JavaScript modern syntax.

// ONLINE-RUNNER:browser;

const areEqual = (array1, array2) => {
    if (array1 === array2) return true;
    if (array1.length !== array2.length) return false;

    for (let i = 0; i < array1.length; ++i) {
        if (array1[i] !== array2[i]) return false;
    }
    return true;
};


// Usage example

console.log(areEqual([1, 2, 3], [1, 2, 3])); // true
console.log(areEqual([1, 2, 3], [3, 2, 1])); // false