performance comparison of different loop technics

loops.js

var size = 10e6, // array size - the larger the better 
    // http://javascriptweblog.wordpress.com/2011/08/08/fixing-the-javascript-typeof-operator/
    toType = function(obj) {
      return ({}).toString.call(obj).match(/\s([a-z|A-Z]+)/)[1].toLowerCase();
    },
    // modify function used in loop peration
    modifyFn = function(val) {
      return val * 2;  
    },
    // caching initialisation result for repeated use
    memo = function (fn) {
        var cache = {};
        return function () {
            var key = [].join.call(arguments, '§') + '§';
            if (!(key in cache)) {
                cache[key] = fn.apply(this, arguments);            
            }
            // arrays keep references to their values, therefore the result array needs to be cloned!
            // otherwise returning the original result array would cause a side effect!
            if (toType(cache[key]) === "array") {
                return cache[key].slice();   
            } else {
                return cache[key];
            }
        };              
    };

function init(size) {
    console.time("init array");
    var result = [];
    for (var i=0; i < size; i++) {
     result.push(i);   
    }
    console.timeEnd("init array");
    return result;
}

cachedInit = memo(init);

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("for loop - array.length access");
    for (var i=0; i<testArr.length; i++) {
        testArr[i] = modifyFn(testArr[i]);
    }
    console.timeEnd("for loop - array.length access");
    //console.log(testArr);
}());

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("for loop - array.length saved");
    for (var i=0, len=testArr.length; i<len; i++) {
        testArr[i] = modifyFn(testArr[i]);
    }
    console.timeEnd("for loop - array.length saved");
    //console.log(testArr);
}());

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("while loop");
    var i = 0, len = testArr.length;
    while (i < len) {
        testArr[i] = modifyFn(testArr[i]);
        i++;
    }
    console.timeEnd("while loop");
    //console.log(testArr);
}());

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("do while loop");
    var i = 0, len = testArr.length;
    do {
        testArr[i] = modifyFn(testArr[i]);
        i++;
    } while (i < len)
    console.timeEnd("do while loop");
    //console.log(testArr);
}());

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("forEach loop");
    testArr.forEach(function(index, element) {
        testArr[index] = modifyFn(element);
    });
    console.timeEnd("forEach loop");
    //console.log(testArr);
}());

(function(){
    var testArr = cachedInit(size);
    //console.log(testArr);
    console.time("map loop");
    testArr.map(function(element) {
        return modifyFn(element);
    });
    console.timeEnd("map loop");
    //console.log(testArr);
}());