//正常base64轉文件上傳
//換成blob上傳
base64UrlToBlob(urlData) {
            let arr = urlData.split(','),
                mime = arr[0].match(/:(.*?);/)[1],  // 去掉url的頭，并轉化為byte
                bstr = atob(arr[1]),    // 處理異常,將ascii碼小于0的轉換為大于0
                n = bstr.length,
                u8arr = new Uint8Array(n);
            while (n--) {
                u8arr[n] = bstr.charCodeAt(n);
            }
            return new Blob([u8arr], { type: mime });
            //轉file
            //return new File([u8arr], filename, {type:mime});
        },

var bl=this.base64UrlToBlob(this.avatar);
var formData=new FormData();
let fileOfBlob = new File([bl], new Date().getTime()+'.jpg');
formData.append("avatar", fileOfBlob);