loopPerfTest.js

function someOperation(x) { }
function looped(array, op) {
    var i, length = array.length;
    for (i = 0; i < length; i++) {
        op(array[i]);
    }
}

function mapped(array, op) {
    array.forEach(op);
}

function timeIt(n, m, crawler, op) {
    var array = new Array(m), i, start, elapsed;

    // jit the crawler
    crawler(array, op);
    start = Date.now();
    for (i = 0; i < n; i++) {
        crawler(array, someOperation);
    }
    elapsed = Date.now() - start;
    print('time:', elapsed);
}

timeIt(100000, 0, looped, someOperation);
timeIt(100000, 0, mapped, someOperation);