实例讲解javascript实现异步图片上传方法

<form id="uploadForm" action="http://storage.test.com/file/upload" method="post" enctype="multipart/form-data">  <input type="hidden" name="key" id="key" value="VTZ18HM64#D_L3WX" />  <input type="file" name="uploadFiles" value="" id="fileImage" multiple='multiple' />  <div class="upload_submit">  <button type="button" id="fileSubmit" class="upload_btn">保存</button>  </div></form>

var Fileupload = {  fileInput: $("#fileImage").get(0),  dragDrop: $("#fileDragArea").get(0),  upButton: $("#fileSubmit").get(0),  url: $("#uploadForm").attr("action"),  })(),  //文件上传  funUploadFile: function() {   var self = this;   for (var i = 0, file; file = this.fileFilter[i]; i++) {    (function(file) {     var xhr = new XMLHttpRequest();     if (xhr.upload) {      // 上传中      xhr.upload.addEventListener("progress", function(e) {       self.onProgress(file, e.loaded, e.total);      }, false);      // 文件上传成功或是失败      xhr.onreadystatechange = function(e) {      if (xhr.readyState == 4) {        if (xhr.status == 200) {         self.onSuccess(JSON.parse(xhr.responseText));         self.funDeleteFile(file);         if (!self.fileFilter.length) {          //全部完毕          self.onComplete();         }        } else {         self.onFailure(file, xhr.responseText);        }       }      };      //准备FormData对象      var myForm = document.getElementById('uploadForm');      //将文件放入FormData对象中      formData = new FormData(myForm);      // 开始上传      xhr.open("POST", self.url, true);      xhr.send(formData);     }    })(file);   }  },  init: function() {   var self = this；   //上传按钮提交   if (this.upButton) {    console.log('提示： 当前存储服务器地址', this.url)    this.upButton.addEventListener("click", function(e) {     self.funUploadFile(e);    }, false);   }   self.bindEvent();  } }; Fileupload = $.extend(Fileupload); Fileupload.init();

<input type="file" id="file">

//准备FormData对象var formData = new FormData(), uploadFile = document.getElementById('file'); //将文件放入FormData对象中 formData.append('file', uploadFile.files[0]);

//创建xhr对象var xhr = new XMLHttpRequest();//监听文件上传进度xhr.upload.onprogress = function(evt){ //lengthComputabel: 文件长度是否可计算 if(evt.lengthComputable){  //evt.loaded: 已下载的字节数  //evt.total: 文件总字节数  var percent = Math.round(evt.loaded*100/evt.total);  console.log(percent); }}//监听文件传输开始 xhr.onloadstart = function(evt）{  xhr.abort() //终止上传}//监听ajax成功完成事件xhr.onload = function(evt){ ...}//监听ajax错误事件 xhr.onerror = function(evt){ ...}//监听ajax被中止事件xhr.onabort = function(evt){ ...}//监听传输结束事件: 不管成功或者失败都会触发xhr.onloaded = function(evt){ ...} //*发起ajax请求数据xhr.open('POST', '/url', true);xhr.send(formData);