Javascript Map, ForI, ForOf, ForIn, ForEach and MapPromise benchmark

Array benchmark.js

(() => {
	function n() {
		let length = Math.floor((Math.random() * 90) + 10);
		let buffer = "";
		for (let i = 0; i < length; i ++) {
			let tmp = Math.floor(Math.random() * 26);
			buffer += String.fromCharCode(65 + tmp);
		}
		
		return buffer;
	}
	
	console.log("Mounting the array...");
	let array = [];
	for (let i = 0; i < 1000000; i ++) {
		array.push(n());
	}
	console.log("Array with " + array.length + " entries!");

	function f (x) { 
		let t = x.length / 2;
		let a = x.substring(0, t);
		let b = x.substring(t);
		return a + b;
	}

	let tmp = [];

	console.time("map");
	tmp = array.map(f);
	console.timeEnd("map");

	tmp = [];
	console.time("fori");
	for (let i = 0; i < array.length; i++) {
		tmp.push(f(array[i]));
	}
	console.timeEnd("fori");

	tmp = [];
	console.time("forof");
	for (let x of array) {
		tmp.push(f(x));
	}
	console.timeEnd("forof");
	
	tmp = [];
	console.time("forin");
	for (let x in array) {
		if (array.hasOwnProperty(x));
		tmp.push(f(array[x]));
	}
	console.timeEnd("forin");

	tmp = [];
	console.time("foreach");
	array.forEach(x => tmp.push(f(x)));
	console.timeEnd("foreach");
	
	console.time("map-promise")	
	Promise.all(
		array.map(x => {
			return new Promise((resolve, reject) => {
				resolve(f(x))
			})
		})
	).then(x => console.timeEnd("map-promise"));
	
}) ();

Results on my machine:

map:         898.11ms
fori:        265.51ms
forof:       286.88ms
forin:       439.98ms
foreach:     279.02ms
map-promise: 2753.61ms