使用JS验证上传文件大小的两种兼容方案

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
  <head> 
  <meta name="DEscription" contect="my code demo" /> 
  <meta name="Author" contect="Michael@www.micmiu.com" /> 
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
  <title>js check file size @ www.micmiu.com</title> 
  </head> 
  <body> 
    <img id="tempimg" dynsrc="" src="" style="display:none" /> 
    <input type="file" name="file" id="fileuploade" size="40" /> 
    <input type="button" name ="check" value="checkfilesize" onclick="checkfile()"/> 
 
  </body> 
  <script type="text/javascript"> 
    var maxsize = 2*1024*1024;//2M 
    var errMsg = "上传的附件文件不能超过2M！！！"; 
    var tipMsg = "您的浏览器暂不支持计算上传文件的大小，确保上传文件不要超过2M，建议使用IE、FireFox、Chrome浏览器。"; 
    var browserCfg = {}; 
    var ua = window.navigator.userAgent; 
    if (ua.indexOf("MSIE")>=1){ 
      browserCfg.ie = true; 
    }else if(ua.indexOf("Firefox")>=1){ 
      browserCfg.firefox = true; 
    }else if(ua.indexOf("Chrome")>=1){ 
      browserCfg.chrome = true; 
    } 
    function checkfile(){ 
      try{ 
        var obj_file = document.getElementById("fileuploade"); 
        if(obj_file.value==""){ 
          alert("请先选择上传文件"); 
          return; 
        } 
        var filesize = 0; 
        if(browserCfg.firefox || browserCfg.chrome ){ 
          filesize = obj_file.files[0].size; 
        }else if(browserCfg.ie){ 
          var obj_img = document.getElementById('tempimg'); 
          obj_img.dynsrc=obj_file.value; 
          filesize = obj_img.fileSize; 
        }else{ 
          alert(tipMsg); 
        return; 
        } 
        if(filesize==-1){ 
          alert(tipMsg); 
          return; 
        }else if(filesize>maxsize){ 
          alert(errMsg); 
          return; 
        }else{ 
          alert("文件大小符合要求"); 
          return; 
        } 
      }catch(e){ 
        alert(e); 
      } 
    } 
  </script> 
</html>