<div id="imgbox">     <img id="imghead" src="img/no_photo.gif" alt="" width="100" height="125" />     </div> <asp:FileUpload ID="FileUploadImg" runat="server" onchange='previewImage(this);'                             style="position:relative;left:-130px;cursor:pointer;"/> var $$ = function(id) {     return "string" == typeof id ? document.getElementById(id) : id; }; /* 图片验证 */ //验证上传图片格式 function checkupload(ele) {     var obj = $$("FileUploadImg");     var fileContentType = obj.value.match(/^(.*)(\.)(.{1,8})$/)[3]; //这个文件类型正则很有用：）        if (fileContentType == 'gif' || fileContentType == 'jpeg' || fileContentType == 'png' || fileContentType == 'jpg') {         //验证上传图片大小         return checkFileSize(ele);     } else {         alert('上传文件格式不正确!');         return false;     }     return false; } //验证上传图片大小 function checkFileSize(ele) {     var maxSize = 100 * 1024;     //ie     if (window.navigator.userAgent.indexOf("MSIE") >= 1) {         var fso;         try {             fso = new ActiveXObject('Scripting.FileSystemObject');             var file = fso.GetFile(ele.value);             //alert(file.Size);             return file.Size < maxSize;         } catch (e) {             alert("浏览器设置禁用ActiveXObject控件，请启用");             return false;         }     }     //firefox     else if (window.navigator.userAgent.indexOf("Firefox") >= 1) {         //alert(ele.files[0].fileSize);         return ele.files[0].fileSize < maxSize;     }     return false; } //加载预览图片 function previewImage(ele) {     if (ele && checkupload(ele)) {         var imgDiv = $$("imgbox");         imgDiv.innerHTML = "";         imgDiv.style.width = "100px";         imgDiv.style.height = "125px";         //ie         if (window.navigator.userAgent.indexOf("MSIE") >= 1) {             imgDiv.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod = scale)";             imgDiv.filters("DXImageTransform.Microsoft.AlphaImageLoader").src = ele.value;         }         //firefox         else if (window.navigator.userAgent.indexOf("Firefox") >= 1) {             imgDiv.innerHTML = "<img width='" + 100 + "' height='" + 125 + "' id='aPic' src='" + ele.files.item(0).getAsDataURL() + "'>";         } else {             imgDiv.innerHTML = "<span style='color:red;'>IE/火狐浏览器才支持图片预览</span>";         }     } else {         $$("FileUploadImg").value = "";         $$("imgbox").innerHTML = "<img id='imghead' src='img/no_photo.gif' alt='' width='100' height='125' />";         //alert('重置上传控件');     } }