javaScript校验图片大小、格式

1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 <script src="/js/jquery-1.4.2.min.js" type="text/javascript"></script>
 <script type="text/javascript">
     $(document).ready(
             function() {
                 $("#form01").change(
                         function() {
                             var filepath = $("input[name='myFile']").val();
                             var extStart = filepath.lastIndexOf(".");
                             var ext = filepath.substring(extStart,
                                     filepath.length).toUpperCase();
                             if (ext != ".BMP" && ext != ".PNG" && ext != ".GIF"
                                     && ext != ".JPG" && ext != ".JPEG") {
                                 alert("图片限于bmp,png,gif,jpeg,jpg格式");
                                 return false;
                             } else {
                                 $("#name01").text(ext)
                             }
                             var file_size = 0;
                             if ($.browser.msie) {
                                 var img = new Image();
                                 img.src = filepath;
                                 while (true) {
                                     if (img.fileSize > 0) {
                                         if (img.fileSize > 3 * 1024 * 1024) {
                                             alert("图片不大于100MB。");
                                         } else {
                                             var num03 = img.fileSize / 1024;
                                             num04 = num03.toFixed(2)
                                             $(".size02").text(num04 + "KB");
                                         }
                                         break;
                                     }
                                 }
                             } else {
                                 file_size = this.files[0].size;
                                 console.log(file_size / 1024 / 1024 + " MB");
                                 var size = file_size / 1024;
                                 if (size > 10240) {
                                     alert("上传的文件大小不能超过10M！");
                                 } else {
                                     var num01 = file_size / 1024;
                                     num02 = num01.toFixed(2)
                                     $("#size01").text(num02 + " KB");
                                 }
                             }
                             return true;
                         });
             });
 </script>
 <title>无标题文档</title>
 </head>
 <body>
     <table width="500" cellspacing="0" cellpadding="0">
         <tr>
             <td width="72" id="name01"></td>
             <td width="242"><input type="file" name="myFile" id="form01" /></td>
             <td width="184" id="size01" class="size02"></td>
         </tr>
     </table>
 </body>
 </html>