用file标签实现多图文件上传预览

<script> 
 //下面用于多图片上传预览功能
 function setImagePreviews(avalue) {
 var docObj = document.getElementById("files");
 var dd = document.getElementById("preview");
 dd.innerHTML = "";
 var fileList = docObj.files;
 for (var i = 0; i < fileList.length; i++) {
 dd.innerHTML += "<div style='float:left' > <img id='img" + i + "' /> </div>";
 var imgObjPreview = document.getElementById("img"+i);
 if (docObj.files && docObj.files[i]) {
 //火狐下，直接设img属性
 imgObjPreview.style.display = 'block';
 //控制缩略图大小
 imgObjPreview.style.width = '70px';
 imgObjPreview.style.height = '70px';
 //imgObjPreview.src = docObj.files[0].getAsDataURL();
 //火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式
 imgObjPreview.src = window.URL.createObjectURL(docObj.files[i]);
 }
 else {
 //IE下，使用滤镜
 docObj.select();
 var imgSrc = document.selection.createRange().text;
 alert(imgSrc)
 var localImagId = document.getElementById("img" + i);
 //必须设置初始大小
 localImagId.style.width = "70px";
 localImagId.style.height = "70px";
 //图片异常的捕捉，防止用户修改后缀来伪造图片
 try {
  localImagId.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
  localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
 }
 catch (e) {
  alert("您上传的图片格式不正确，请重新选择!");
  return false;
 }
 imgObjPreview.style.display = 'none';
 document.selection.empty();
 }
 }
 return true;
 }
 </script>

<form method="post" enctype="multipart/form-data"> 
 <input type="file" accept="image/png,image/gif,image/jpg,image/jpeg" id="files" name="files" multiple onchange="javascript:setImagePreviews();" />
 <input type="button" id="upload" value="上传" />
 <div id="preview"> 
 </div> 
</form>