for vs foreach

arrben.js

/**
$ node --version
v7.10.0

$ node arrben.js
foreach 2294.22208
for 1342.5684099999999
*/

const benchmark = (name, fn, n = 100) => {
	const startTime = process.hrtime();
	for(var i = 0; i < n; i++) {
		fn();
	}
	const diff = process.hrtime(startTime);
	const usec = diff[0] * 1e9 + diff[1];
	const time = (usec / 1000) / n;
	console.log(name, time);
};

const arr = new Array(100000).fill(null).map((v, i) => i);

const fa = () => {
	const a = arr;
	let x = 0;
	a.forEach((v) => {
		if(v % 8 === 0) x += v;
	});
	return x;
};

const fb = () => {
	const a = arr, l = a.length;
	let x = 0;
	for(var i = 0; i < l; i++) {
		if(a[i] % 8 === 0) x += a[i];
	}
	return x;
};

benchmark('foreach', fa);
benchmark('for', fb);