Benchmarking javascript loop performance

gistfile1.txt

Install `benchmark` (https://benchmarkjs.com/) and run:

    npm install --save benchmark
    node loopperf.js

loopperf.js

const benchmark = require('benchmark');
const suite = new benchmark.Suite();

let array = Array(10000).fill(undefined).map((_, i) => i);

suite.add("for loop: i < array.length",
         function() {
	         for (let i = 0; i < array.length; i++)
		         array[i];
         })
    .add("for loop: i < presaved length",
         function() {
	         var count = array.length;
	         for (let i = 0; i < count; i++) {
		         array[i];
	         }
         })
    .add("for loop: i < inline length (Zakas HPJS)",
         function() {
	         for (let i = 0, count = array.length; i < count; i++) {
		         array[i];
	         }
         })
    .add("for loop: reversed (Zakas HPJS)",
         function() {
	         for (let i = array.length; i--; )
		         array[i];
         })
    .add("forEach",
         function() {
	         array.forEach(elt => elt);
         })
    .add("map",
         function() {
	         array.map(elt => elt);
         })
    .on("cycle", function(event) {
	    console.log(String(event.target));
       })
    .on("complete", function() {
        console.log("Fastest is " + this.filter('fastest').map('name'));
       })
    .run({ 'async' : true });