How to Sort Array of Numbers in JavaScript Quickly and Correctly

To sort an array of numbers in JavaScript, use the sort() method with a compare function like (a, b) => a - b. This ensures numbers are sorted in numeric order instead of as strings.

Syntax

The sort() method sorts the elements of an array in place and returns the sorted array. When sorting numbers, you should provide a compare function to define the sort order.

• array.sort(compareFunction): Sorts the array using the compareFunction.
• compareFunction(a, b): Returns a negative number if a should come before b, zero if they are equal, or a positive number if a should come after b.

javascript

array.sort((a, b) => a - b);

Example

This example shows how to sort an array of numbers in ascending order using the sort() method with a compare function.

javascript

const numbers = [40, 100, 1, 5, 25, 10];
numbers.sort((a, b) => a - b);
console.log(numbers);

Output

[1, 5, 10, 25, 40, 100]

Common Pitfalls

Without a compare function, sort() converts numbers to strings and sorts them lexicographically, which leads to incorrect order for numbers.

For example, [40, 100, 1].sort() results in [1, 100, 40], which is wrong numerically.

javascript

const arr = [40, 100, 1];
console.log(arr.sort()); // Wrong: [1, 100, 40]

// Correct way:
console.log(arr.sort((a, b) => a - b)); // Correct: [1, 40, 100]

Output

[1, 100, 40]
[1, 40, 100]

Quick Reference

• Use: array.sort((a, b) => a - b) for ascending numeric sort.
• Use: array.sort((a, b) => b - a) for descending numeric sort.
• Remember: Without a compare function, numbers sort as strings.

Key Takeaways

Always provide a compare function to sort numbers correctly in JavaScript.

The compare function should return a negative, zero, or positive value to define order.

Without a compare function, numbers are sorted as strings, causing wrong order.

Use (a, b) => a - b for ascending and (a, b) => b - a for descending numeric sort.