js 图片上传前大小长宽验证代码

脚本如下：
<html> <head> <script language="javascript" type="text/javascript"> function getimginfo() { var img=new Image(); img.src=document.all.file.value; var sInfo="Width:"+img.width+ "px Height:"+img.height+ "px Size:"+getsizestring(img.fileSize); alert(sInfo); } function getsizestring(len) { var kb=len/1024; if(kb<1024) return kb.toFixed(2)+"K"; else { var m=kb/1024; return m.toFixed(2)+"M"; } } </script> </head> <body> <table width="90%" border="0" cellspacing="0" cellpadding="0"> <tr> <td> <img width="60" height="60" id="picdemo"> </td> <td> <input type="file" id="file" onchange="document.all.picdemo.src=this.value" class="allinput">  <input type="submit" name="Submit" value="上传" onClick="getimginfo();"> </td> </tr> </table> </body> </html>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]