js 验证(判断)是否为网址

<code> 
 
<script language="JavaScript"> 
<!-- 
function Validate(form) { 
    var v = new RegExp(); 
    v.compile("^[A-Za-z]+://[A-Za-z0-9-_]+\\.[A-Za-z0-9-_%&\?\/.=]+$"); 
    if (!v.test(form["URL"].value)) { 
        alert("You must supply a valid URL."); 
        return false; 
    } 
} 
//--> 
</script> 
 
 
<form name="MyForm" action="" method="POST" onsubmit="return Validate(this);"> 
<input type="TEXT" name="URL" value="http://"> 
<input type="SUBMIT" name="SUBMIT" value="SUBMIT"> 
</form> 
 
</code>