How to Sort an Array of Numbers in JavaScript

Sorting numbers in JavaScript requires special attention because the Array.prototype.sort() method treats array elements as strings by default.

Example: Basic Sorting

Here’s a step-by-step example:

let numbers = [40, 1, 5, 200];

// Ascending order
numbers.sort((a, b) => a - b);
console.log(numbers); // Output: [1, 5, 40, 200]

// Descending order
numbers.sort((a, b) => b - a);
console.log(numbers); // Output: [200, 40, 5, 1]

Explanation

The Problem with Default Sorting

• numbers.sort();
• This will result in [1, 200, 40, 5].
• Why? Because sort() converts numbers to strings and sorts them lexicographically (e.g., “200” comes before “40”).

Using a Compare Function

• To sort numbers correctly, pass a compare function to sort().The function a - b ensures:
  • Ascending Order: If a < b, it returns a negative value.
  • Descending Order: If b < a, it returns a positive value.

Use Case: Sorting a Mixed Array

If the array contains non-numeric values, you’ll need to filter or handle them appropriately:

let mixedArray = [40, "apple", 1, 5, 200, "banana"];

// Filter and sort numbers only
let sortedNumbers = mixedArray.filter(item => typeof item === "number").sort((a, b) => a - b);
console.log(sortedNumbers); // Output: [1, 5, 40, 200]

Sorting in Reverse

For reversing any sorted array:

let numbers = [1, 5, 40, 200];
numbers.reverse();
console.log(numbers); // Output: [200, 40, 5, 1]

Key Points to Remember

• Always provide a compare function for numeric sorting.
• Use filter() if the array contains mixed types.
• Use reverse() for reversing the order after sorting.