在做图片上传功能的时候，遇到了JS无法识别图片type的问题，在使用过程中是没有问题的，但是不知道为什么浏览器的Console报这个错误：

Uncaught TypeError: Cannot read property 'type' of undefinedat Function.$.ImgSrc (ModelUpload.do:18)at uploadImg (ModelUpload.do:77)at HTMLInputElement.onchange (ModelUpload.do:110)

alert下面JS代码中的file[i].type的时候显示的是img/jpeg why？？？
页面相关代码如下：
HTML：

        <p><label for="picFileId">缩略图文件:</label> <input id="picFileId"name="picFileId" type="file" onchange="uploadImg()" /><fieldset><div style="position: relative;" id="fileImg"></div><legend>图片显示区域</legend></fieldset><p>

JS：

<script type="text/javascript">$.ImgSrc = function(file, id) {for (var i = 0; i < 3; i++) {alert(file[i].type);if (!/image\/\w+/.test(file[i].type)) {alert("请选择图片文件");return false;};if (file[i].size > 2048 * 1024) {alert("图片不能大于2M")ClearImg();continue;};var img;console.log(document.getElementById("fileImg"));console.log(file[i]);console.log("file-size=" + file[i].size);var reader = new FileReader();reader.onloadstart = function(e) {console.log("开始读取....");}reader.onprogress = function(e) {console.log("正在读取中....");}reader.onabort = function(e) {console.log("中断读取....");}reader.onerror = function(e) {console.log("读取异常....");}reader.onload = function(e) {console.log("成功读取....");var div = document.createElement("div"); //外层 divdiv.setAttribute("style","position:relative;width:inherit;height:inherit;float:left;z-index:2;width:150px;margin-left:8px;margin-right:8px;");var del = document.createElement("div"); //删除按钮divdel.setAttribute("style","position: absolute; bottom: 4px; right: 0px; z-index: 99; width: 30px; height:30px;border-radius:50%;")var delicon = document.createElement("img");delicon.setAttribute("src", "images/shanchu.png");delicon.setAttribute("title", "删除");delicon.setAttribute("style","cursor:pointer;width: 30px; height:30px");del.onclick = function() {this.parentNode.parentNode.removeChild(this.parentElement);ClearImg();};del.appendChild(delicon);div.appendChild(del);var imgs = document.createElement("img"); //上传的图片imgs.setAttribute("name", "loadimgs");imgs.setAttribute("src", e.target.result);imgs.setAttribute("width", 150);//childNodes.length > 0  代表 最多传一张，再上传，就把前面的替换掉if (document.getElementById(id).childNodes.length > 0) {document.getElementById(id).removeChild(document.getElementById(id).firstChild);}div.appendChild(imgs)document.getElementById(id).appendChild(div);}reader.readAsDataURL(file[i]);}}function uploadImg() {$.ImgSrc(document.getElementById("picFileId").files, "fileImg");}function ClearImg() {var file = $("#picFileId")file.after(file.clone().val(""));file.remove();}
</script>

JS报错：Cannot read property 'type' of undefined >> java

这个答案描述的挺清楚的：
http://www.goodpm.net/postreply/java/1010000008888543/JS报错Cannotreadpropertytypeofundefined.html