How to Efficiently Merge Arrays in JavaScript

Merging arrays is a common task in JavaScript. Whether you’re combining data from multiple sources or simply concatenating lists, JavaScript provides several methods for merging arrays. However, it’s important to choose the most efficient way depending on the size of the arrays and the requirements of your use case.

In this blog, we’ll explore several methods of merging arrays in JavaScript, comparing their efficiency and demonstrating the best approaches.

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1. Using the concat() Method

The concat() method is one of the most straightforward ways to merge two or more arrays. It does not modify the original arrays and returns a new array that contains the combined elements.

Example:

let array1 = [1, 2, 3];
let array2 = [4, 5, 6];

let mergedArray = array1.concat(array2);

console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]

Performance:

• Time Complexity: O(n + m), where n and m are the lengths of the two arrays being merged.
• Space Complexity: O(n + m) because a new array is created.

Pros:

• Simple to use.