js認証URL

js認証URL：

<script language="javascript">      
 function check(str){   
 var checkfiles=new RegExp("((^http)|(^https)|(^ftp)):\/\/(\\w)+\.(\\w)+");
// var checkfiles=new RegExp("^[A-Za-z+]+:\/\/(\\w)+\.(\\w)+");
   if(checkfiles.test(str)){
           alert("  ");
   }
   else{
           alert("   ");
   }    
}  
 </script> 
 
 <input   type="text"   id="txt">      
 <input   type="button" onclick="check(txt.value)" value="check">