REGEX: Capture Filename from URL without file extension

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("."));

Answer 2

Try this regex. It can even handle filenames with multiple periods.

(?<=\/)[^\/]*(?=\.\w+$)

Answer 3

tested and works, even for pages without file extension.

var re = /([\w\d_-]*)\.?[^\\\/]*$/i;

var url = "http://stackoverflow.com/questions/3671522/regex-capture-filename-from-url-without-file-extention";
alert(url.match(re)[1]); // 'regex-capture-filename-from-url-without-file-extention'

url = 'http://gunblad3.blogspot.com/2008/05/uri-url-parsing.html';
alert(url.match(re)[1]); // 'uri-url-parsing'

([\w\d_-]*) get a string containing letters, digits, underscores or hyphens.
\.? perhaps the string is followed by a period.
[^\\\/]*$ but certainly not followed by a slash or backslash till the very end.
/i oh yeh, ignore case.

Answer 4

I did not find any of the answers to be near robust enough. Here is my solution.

function getFileName(url, includeExtension) {
    var matches = url && typeof url.match === "function" && url.match(/\/?([^/.]*)\.?([^/]*)$/);
    if (!matches)
        return null;

    if (includeExtension && matches.length > 2 && matches[2]) {
        return matches.slice(1).join(".");
    }
    return matches[1];
}

var url = "http://example.com/index.htm";
var filename = getFileName(url);
// index
filename = getFileName(url, true);
// index.htm

url = "index.htm";
filename = getFileName(url);
// index
filename = getFileName(url, true);
// index.htm

// BGerrissen's examples
url = "http://stackoverflow.com/questions/3671522/regex-capture-filename-from-url-without-file-extention";
filename = getFileName(url);
// regex-capture-filename-from-url-without-file-extention
filename = getFileName(url, true);
// regex-capture-filename-from-url-without-file-extention

url = "http://gunblad3.blogspot.com/2008/05/uri-url-parsing.html";
filename = getFileName(url);
// uri-url-parsing
filename = getFileName(url, true);
// uri-url-parsing.html

// BGerrissen fails
url = "http://gunblad3.blogspot.com/2008/05/uri%20url-parsing.html";
filename = getFileName(url);
// uri%20url-parsing
filename = getFileName(url, true);
// uri%20url-parsing.html

// George Pantazis multiple dots
url = "http://gunblad3.blogspot.com/2008/05/foo.global.js";
filename = getFileName(url);
// foo
filename = getFileName(url, true);
// foo.global.js

// Fringe cases
url = {};
filename = getFileName(url);
// null
url = null;
filename = getFileName(url);
// null

To fit with the original question, the default behavior is to exclude the extension, but that can easily be reversed.