JavaScript/EcmaScript loop benchmark (incl. for/for-of/while/forEach/map)

var arr = Array(1000000).fill(null);
var dosmth;

for (let i = 0; i < arr.length; i++) {
    dosmth = arr[i];
}

let len = arr.length;
for (let i = 0; i < len; i++) {
    dosmth = arr[i];
}

for (let val of arr) {
    dosmth = val;
}

let i = 0;

while(i < arr.length){
	dosmth = arr[i];
	++i;
}

let i = 0;
const len = arr.length;

while(i < len){
	dosmth = arr[i];
	++i;
}

arr.forEach(el=>(dosmth = el));

arr.map(el=>(dosmth = el));