for loop comparison - probably poor benchmarking on my part

for.js

(function() {
    let array = [];
    for (let i = 0; i < 10000000; ++i) {
        array.push({
            a: i,
            b: i / 2,
            r: 0,
        });
    }

    function whileLoop() {
        let i = 0;
        while (i < array.length) {
            let x = array[i];
            x.r = x.a + x.b;
            i++;
        }
    }

    function forEach() {
        array.forEach(x => {
            x.r = x.a + x.b;
        });
    }
    
    function forOf() {
        for (let x of array) {
            x.r = x.a + x.b;
        }
    }

    function forIn() {
        for (let i = 0; i < array.length; i++) {
            let x = array[i];
            x.r = x.a + x.b;
        }
    }

    function forInWithCache() {
        for (let i = 0, length = array.length; i < length; i++) {
            let x = array[i];
            x.r = x.a + x.b;
        }
    }

    function timeIt(fn, name) {
        console.log("________", name);
        for (let i = 0; i < 20; i++) {
            let print = i === 0 ? " first time" : i === 19 ? "  optimized" : "";
            print && console.time(name + print);
            fn();
            print && console.timeEnd(name + print);
        }
    }

    timeIt(forOf, "for-of");
    timeIt(forIn, "for-in");
    timeIt(forInWithCache, "for-in w/cache");
    timeIt(forEach, "forEach");
    timeIt(whileLoop, "while loop");
})();