String Functions

I want to find out what is the file name of the page that a user is currently viewing (for e.g. the file name of the page where I am composing this query currently is newthread.php). If the file name is Edit.asp, then do something else......this is the

(this is the onLoad event function)function getFile(){
var strURL=window.location

//since the file name will be at the end of the URL, I am using
//a negative number as the start parameter in the substr function

if(strURL.substr(-9,strURL.length)=="Edit.asp"){
//do something
}
else{
//do something else
}
}

But the above doesn't work. In fact, some of the JavaScript string functions I tried (like match, length etc.), none of them seem to work since the string has been derived using window.location. Why? Doesn't JavaScript consider the URL of a page as a string object?