    // 所有文件的进度信息，key为file id
                percentages = {},
                // 判断浏览器是否支持图片的base64
                isSupportBase64 = (function () {
                    var data = new Image();
                    var support = true;
                    data.onload = data.onerror = function () {
                        if (this.width != 1 || this.height != 1) {
                            support = false;
                        }
                    }
         