Question

I am trying to create a Javascript Regex that captures the filename without the file extension. I have read the other posts here and ‘goto this page: http://gunblad3.blogspot.com/2008/05/uri-url-parsing.html‘ seems to be the default answer. This doesn’t seem to do the job for me. So here is how I’m trying to get the regex to work:

1. Find the last forward slash ‘/’ in the subject string.
2. Capture everything between that slash and the next period.

The closest I could get was : /([^/]).\w$ Which on the string ‘http://example.com/index.htm‘ exec() would capture /index.htm and index.

I need this to only capture index.

Answer 1

var url = "http://example.com/index.htm";
var filename = url.match(/([^\/]+)(?=\.\w+$)/)[0];

Let’s go through the regular expression:

[^\/]+    # one or more character that isn't a slash
(?=       # open a positive lookahead assertion
  \.      # a literal dot character
  \w+     # one or more word characters
  $       # end of string boundary
)         # end of the lookahead

This expression will collect all characters that aren’t a slash that are immediately followed (thanks to the lookahead) by an extension and the end of the string — or, in other words, everything after the last slash and until the extension.

Alternately, you can do this without regular expressions altogether, by finding the position of the last / and the last . using lastIndexOf and getting a substring between those points:

var url = "http://example.com/index.htm";
var filename = url.substring(url.lastIndexOf("/") + 1, url.lastIndexOf("."));