同时兼容IE和FF的图片上传判断及预览脚本

<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');    }}