XMLHttpRequest + FormData图片上传

uploadPic.js

 /**
 * let formData = new FormData();
 * for (let i = 0; i < this.files.length; i++) {
      formData.append("file", this.files[i], this.files[i].name);
  }
 */
 
 uploadPic(formData){
         let jwt = localStorage["jwt"];
         /*let headers = new Headers({
             'Content-Type': 'multipart/form-data',
             'Authorization': "Bearer " + jwt
         });
         let options = new RequestOptions({headers: headers});

         return this.http.post(this.uploadUrl, formData, options)
         .toPromise()
         .then(this.extractData)
         .catch(this.handleError);*/

        let xhr = new XMLHttpRequest();


        return new Promise((resolve, reject) => {
            xhr.onreadystatechange = () => {
                if (xhr.readyState == 4) {
                    if (xhr.status >= 200 && xhr.status < 300)
                        resolve({xhr: xhr, formData: formData});
                    else
                        reject({xhr: xhr, formData: formData});

                }
            };

            xhr.open('POST', this.uploadUrl, true);
            xhr.setRequestHeader("Authorization", "Bearer " + jwt);
            xhr.send(formData);
        });
    }