JS批量打包下載圖片（筆記）

 <img src="http://img.zcool.cn/community/01c92f56597f686ac7251c94e76e51.jpg" />
 <img src="http://img.zcool.cn/community/01888f5922bad7b5b3086ed4cc3711.jpg" />
 <button onclick="packageImages()">packageImages</button><span id="status"></span>

<script src="http://stuk.github.io/jszip/test/jquery-1.8.3.min.js"></script>
<script type="text/javascript" src="https://stuk.github.io/jszip/dist/jszip.js"></script>
<script type="text/javascript" src="http://stuk.github.io/jszip/vendor/FileSaver.js"></script>

function packageImages() {
    $('#status').text('處理中。。。。。');

    var imgs = $('img');

    var imgsSrc = [];
    var imgBase64 = [];
    var imageSuffix = [];//圖片后綴
    var zip = new JSZip();
    zip.file("readme.txt", "案件詳情資料\n");
    var img = zip.folder("images");

    for (var i = 0; i < imgs.length; i++) {
        var src = imgs[i].getAttribute("src");
        var suffix = src.substring(src.lastIndexOf("."));
        imageSuffix.push(suffix);

        getBase64(imgs[i].getAttribute("src"))
            .then(function (base64) {
                imgBase64.push(base64.substring(22));

                //console.log(base64);//處理成功打印在控制台
            }, function (err) {
                console.log(err);//打印異常信息
            });

    }
    function tt() {
        setTimeout(function () {
            if (imgs.length == imgBase64.length) {
                for (var i = 0; i < imgs.length; i++) {
                    img.file(i + imageSuffix[i], imgBase64[i], { base64: true });
                }
                zip.generateAsync({ type: "blob" }).then(function (content) {
                    // see FileSaver.js
                    saveAs(content, "images.zip");
                });
                $('#status').text('處理完成。。。。。');

            } else {
                //console.log('imgs.length:'+imgs.length+',imgBase64.length:'+imgBase64.length);
                $('#status').text('已完成：' + imgBase64.length + '/' + imgs.length);
                tt();
            }
        }, 100);

    }
    tt();
}

//傳入圖片路徑，返回base64
function getBase64(img) {
    function getBase64Image(img, width, height) {//width、height調用時傳入具體像素值，控制大小 ,不傳則默認圖像大小
        var canvas = document.createElement("canvas");
        canvas.width = width ? width : img.width;
        canvas.height = height ? height : img.height;

        var ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
        var dataURL = canvas.toDataURL();
        return dataURL;
    }
    var image = new Image();
    image.crossOrigin = 'Anonymous';
    image.src = img;
    var deferred = $.Deferred();
    if (img) {
        image.onload = function () {
            deferred.resolve(getBase64Image(image));//將base64傳給done上傳處理
        }
        return deferred.promise();//問題要讓onload完成后再return sessionStorage['imgTest']
    }
}