md5 calculation for files in javascript

$(document).ready(function () {
    $("#btnUpload").click(function (evt) {
        var fl = document.getElementById("files");
        var L = fl.files.length;
        for (var i = 0; i < L ; i++) {
            var file = fl.files[i];
            var file = fl.files[i];
    calcMD5(file);
    var bytes_per_chunk = 1024 * 1024; //1048576
    var start = 0;
    var end = bytes_per_chunk;
    var size = file.size;
    var j = bytes_per_chunk;
    while (start < size) {
        //push the fragments to an array
        blobs.push(file.slice(start, end));
        start = j;
        j = start + bytes_per_chunk;;
        end = start + bytes_per_chunk;
        if (end > size) {
            end = size;
        }
    }
    var fileName = file.name;
    var fileType = file.type;
    var fileUp = (100 * bytes_per_chunk) / file.size;
    var rec = 0;
    var count = 0;
    var temp = 0;
    while (blob = blobs.shift()) {
        rec = fileUp + rec;
        if (rec > 100) {
            rec = 100;
        }
        xhr.open('POST', 'FileUploadHandler.ashx', false);
        xhr.setRequestHeader('X_FILE_NAME', fileName);
        xhr.setRequestHeader('Content-Type', fileType);
        xhr.send(blob);
        count++;
        }
    });
});

function calcMD5(f) {
    // MD5 Calculation
    var blobSlice = File.prototype.slice || File.prototype.mozSlice || File.prototype.webkitSlice,
    file = f,
    chunkSize = 1024 * 1024,                             // Read in chunks of 2MB
    chunks = Math.ceil(file.size / chunkSize),
    currentChunk = 0,
    spark = new SparkMD5.ArrayBuffer(),
    fileReader = new FileReader();

    fileReader.onload = function (e) {
        console.log('read chunk nr', currentChunk + 1, 'of', chunks);
        spark.append(e.target.result);                   // Append array buffer
        currentChunk++;

        if (currentChunk < chunks) {
            loadNext();
        } else {
            console.log('finished loading');
            console.info('computed hash', spark.end());  // Compute hash
        }
    };

    fileReader.onerror = function () {
        console.warn('oops, something went wrong.');
    };
    function loadNext() {
        var start = currentChunk * chunkSize,
            end = ((start + chunkSize) >= file.size) ? file.size : start + chunkSize;

        fileReader.readAsArrayBuffer(blobSlice.call(file, start, end));
    }
    loadNext();
}