How to Sort an Array in JavaScript

In this tutorial, we’ll learn how to sort an Array in JavaScript by using Array.sort() method.

Sort String Array

Let’s create a string array:

const fruits = ['mango', 'cherry', 'berries', 'apple', 'banana', 'kiwi'];

We can sort the array elements in ascending alphabetical (a-z, A-Z) order using sort() method:

fruits.sort();
console.log(fruits);

▶ (6) ["apple", "banana", "berries", "cherry", "kiwi", "mango"]

We can also sort the array elements in descending alphabetical (z-a, Z-A) order using reverse() method:

fruits.reverse();
console.log(fruits);

▶ (6) ["mango", "kiwi", "cherry", "berries", "banana", "apple"]

Sort Number Array

The built-in sort() and reverse() methods sort the array elements in alphabetical order so it is not useful when it comes to number array. Fortunately, sort() methods takes compare functions as an argument which can be used to override its default sorting behavior.

Let’s first create our compare function:

Compare Function

function(a, b) {return a - b}

When the sort() method compares two values, it sends the values to our compare function and sorts the values according to the returned value.

• If the result is negative, a is sorted before b.
• If the result is positive, b is sorted before a.
• If the result is 0, nothing changes.

Let’s sort number array in ascending order using sort() with compare function:

const numbers = [1, 7, 3, 5, 8, 2, 9, 4, 6];

numbers.sort(function(a, b){return a - b});     //ascending
console.log(numbers);

▶ (9) [1, 2, 3, 4, 5, 6, 7, 8, 9]

We need to reverse the subtraction from (a - b) to (b - a) in compare function, if we want to sort the numbers in descending order:

const numbers = [1, 7, 3, 5, 8, 2, 9, 4, 6];

numbers.sort(function(a, b){return b - a});    //descending
console.log(numbers);

▶ (9) [9, 8, 7, 6, 5, 4, 3, 2, 1]