This snippet will get the filename from the url. The filename is the last part of the URL from the last trailing slash. For example, if the URL is http://www.example.com/dir/file.html then file.html is the file name.

Explanation

var url = window.location.pathname;

This declares the url variable and adds the current pathname as its value.

var filename = url.substring(url.lastIndexOf('/')+1);
alert(filename);

substring (method) - extract characters from start (parameter). url is the stringObject url.substring(start)

lastIndexOf (method) - position of last occurrence of specified string value, in this case the ‘/’

Add one to lastIndexOf because we do not want to return the ‘/’

Full snippet

var url = window.location.pathname;
var filename = url.substring(url.lastIndexOf('/')+1);
alert(filename);