JavaScript Loops performance

TL;DR

for loop is fastest

Code

Code is pretty simple and straightforward. I created an array with 10000000 length and filled it in with zeros.

const arr = new Array(10000000).fill(0);

After that I created function for every loop that iterates over items, and pushes current item to array. performance API is used for measuring performance, since it is most accurate. Here is an example for for loop

let resFor = [];

const startFor = performance.now();

for (let i = 0; i < arr?.length; i++) {
  resFor.push(i);
}

const endFor = performance.now();

console.log("For loop: ", endFor - startFor);

Hardware and testing

I am using MacBook Pro 13-inch M1 2020 for testing. Every function is running for 5 times, and average value is taken from all those runs.

Notes

As you can see on the graph, for loop is the fastest, but only on big array of items. I tested same code on 100, 1000, and 10000 items, and performance difference wasn't big at all, which means that on smaller arrays (up to 10000 items) there isn't much reason to optimize loops.

Don't take these tests as only source of truth. Results can and will vary based on you hardware, data that you are looping over and others, but for loop will be fastest in most cases.