javascript判断文件是否存在
1. 客户端

<script language="javascript">function FileExist(){      var sfso=new ActiveXObject("Scripting.FileSystemObject");     var fPath="[The path of the file]";     if(sfso.FileExists(fPath))     {          alert("Exist");     }     else     {          alert("Doesn't exist");     }}</script> 

<script language="javascript">function FileExist(){     var xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");     xmlhttp.open("GET",FileURL,false);     xmlhttp.send();     if(xmlhttp.readyState==4)     {             if(xmlhttp.status==200) alert("Exist");             else if(xmlhttp.status==404) alert("Doesn't exist");          else alert("Don't know");       } }</script>