How to Efficiently Sort One Array and Map to Another in JavaScript

Discover how to effectively sort an array in JavaScript and apply the sorted indices to another array, creating a structured and intuitive solution.
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How to Efficiently Sort One Array and Map to Another in JavaScript

Sorting arrays is a common task in programming, and when it comes to JavaScript, the built-in sort() function can be a powerful tool. However, what do you do when you want to sort one array and apply that sorting to a second array? In this guide, we'll explore a simple yet effective solution to this problem.

The Problem

Imagine you have two arrays:

[[See Video to Reveal this Text or Code Snippet]]

Your goal is to sort arr1 in decreasing order and then rearrange arr2 based on the new order of arr1.

After sorting, arr1 would look like this:

[[See Video to Reveal this Text or Code Snippet]]

The indices of the original arr1 items change after sorting as follows:

Original indices: [0, 1, 2, 3, 4]

Sorted indices: [0, 1, 3, 4, 2] (meaning the number 5 from index 3 now goes to index 2 in the sorted array).

The aim is to apply this index mapping to arr2, resulting in:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

While you may have considered more complex solutions using objects or maps, there is a more straightforward approach: zipping the two arrays together, sorting the combined array, and extracting the values back out.

Step-by-Step Guide

Zip the Arrays: Create a new array where each element is a pair consisting of an element from arr1 and its corresponding element from arr2.

Sort the Zipped Array: Use sort() to arrange the pairs based on the values of arr1.

Extract Values: After sorting, separate the values back into their respective arrays.

Here's how to implement this in JavaScript:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Zipping: The map() function combines elements from both arrays into pairs.

Sorting: The sort() function sorts the pairs based on the first element (from arr1) in descending order.

Mapping Back: We use map() again to retrieve the sorted lists.

Conclusion

By zipping the arrays together, sorting them, and then extracting the values, you can efficiently rearrange one array based on the sorted order of another. Not only does this method simplify the process, but it also leverages the power of JavaScript's built-in array functions to produce a clean and effective solution.

Feel free to try this approach in your own code, and see how it can streamline the sorting of arrays and maintain their relationships. Happy coding!