HTML JavaScript Metro style loading bar improved

<!DOCTYPE html>
<html>
    <head>
        <title>HTML Metro Loading Bar</title>
        <style type="text/css">
        body { background: #000 ;}
        .block {
            background: #0fF;
            height: 5px;
            width: 5px;
        }
        </style>
    <head>
    <body>
        <script type="text/javascript">
        LoadingBar = function (args /* { element : document element, numBlocks : integer } */) {

            var args = args == undefined ? { numBlocks: this.numBlocks, element: document.createElement('div')} : args;

            this.numBlocks = args.numBlocks == undefined ? this.numBlocks : typeof args.numBlocks == 'number' ? args.numBlocks : this.numBlocks;
            this.element = args.element == undefined ? document.createElement('div') : args.element;

            this.element.className = 'loading-bar';
            this.element.style.position = 'absolute';
            this.element.style.left = '0';
            this.element.style.right = '0';
            this.element.style.overflow = 'hidden';
            this.setDimensions();
            var _this = this;
            window.addEventListener('resize', function () { _this.setDimensions() });
            return this;
        }

        LoadingBar.prototype = {

            constructor: LoadingBar,
            interval: null,
            loops: 0,
            loopPauseDuration: 1000,
            element: null,
            numBlocks: 5,
            animationSpeed: 10,
            blockDisplacemenetSpeed: 6,
            slowDownPercentage: 50,
            slowDownRange: 0,
            slowDownAreaStart: 0,
            slowDownAreaStop: 0,

            setDimensions: function () {
                this.element.style.width = window.innerWidth + 'px';
                this.slowDownRange = Math.floor((parseInt(this.element.style.width) / 3));
                this.slowDownAreaStart = this.slowDownRange;
                this.slowDownAreaStop = this.slowDownRange * 2;
            },

            addBlock: function () {
                var block = document.createElement('div');
                block.className = 'block';
                block.style.position = 'fixed';
                block.style.display = 'block';
                this.element.appendChild(block);
                return block;
            },

            removeBlock: function (index) {
                this.element.removeChild(this.element.getElementsByClassName('block')[index]);
            },

            clearBlocks: function () {
                while (this.element.hasChildNodes()) {
                    this.element.removeChild(this.element.lastChild);
                }
            },

            start: function () {
                this.reset();
                for (var i = 0; i < this.numBlocks; i++) {
                    this.addBlock().style.left = Math.floor(-1 * (1 + i) * (this.slowDownRange / this.numBlocks)) + 'px';
                }
                var pause = this.loops == 0 ? 0 : this.loopPauseDuration,
                    _this = this;
                this.loops++;
                this.interval = setTimeout(function () { _this.animate(); }, pause);
                return this;
            },

            animate: function () {
                var _this = this,
                    blocks = this.element.getElementsByClassName('block');

                if (blocks.length == 0) return this.start();

                for (var i in blocks) {
                    if (typeof blocks[i] == 'object') {
                        var x = parseInt(blocks[i].style.left),
                            displacementSpeed = this.blockDisplacemenetSpeed;

                        if (x >= this.slowDownAreaStart && x <= this.slowDownAreaStop) {
                            displacementSpeed = Math.floor(displacementSpeed / (100 / this.slowDownPercentage));
                        }
                        blocks[i].style.left = (x + displacementSpeed) + 'px';

                        if (parseInt(blocks[i].style.left) >= parseInt(this.element.style.width)) {
                            this.removeBlock(i)
                        }
                    }
                }
                this.interval = setTimeout(function () { _this.animate(); }, _this.animationSpeed);
            },

            reset: function()
            {
                this.clearBlocks();
                clearTimeout(this.interval);
            },

            stop: function () {
                this.loops = 0;
                this.clearBlocks();
                clearTimeout(this.interval);
            }
        }

        document.body.appendChild(new LoadingBar().start().element);
        </script>
    </body>
</html>