I know there are easier ways to get file extensions with JavaScript, but partly to practice my regexp skills I wanted to try and use a regular expression to split a filename into two strings, before and after the final dot (. character).
Here's what I have so far
const myRegex = /^((?:[^.]+(?:\.)*)+?)(\w+)?$/
const [filename1, extension1] = 'foo.baz.bing.bong'.match(myRegex);
// filename1 = 'foo.baz.bing.'
// extension1 = 'bong'
const [filename, extension] = 'one.two'.match(myRegex);
// filename2 = 'one.'
// extension2 = 'two'
const [filename, extension] = 'noextension'.match(myRegex);
// filename2 = 'noextension'
// extension2 = ''
I've tried to use negative lookahead to say 'only match a literal . if it's followed by a word that ends in, like so, by changing (?:\.)* to (?:\.(?=\w+.))*:
/^((?:[^.]+(?:\.(?=(\w+\.))))*)(\w+)$/gm
But I want to exclude that final period using just the regexp, and preferably have 'noextension' be matched in the initial group, how can I do that with just regexp?
Here is my regexp scratch file: https://regex101.com/r/RTPRNU/1
Just wanted to do a late pitch-in on this because I wanted to split up a filename into a "name" and an "extension" part - and wasn't able to find any good solutions supporting all my test cases ... and I wanted to support filenames starting with "." which should return as the "name" and I wanted to support files without any extension too.
So I'm using this line which handles all my use-cases
const [name, ext] = (filename.match(/(.+)+\.(.+)/) || ['', filename]).slice(1)
Which will give this output
'.htaccess' => ['.htaccess', undefined]
'foo' => ['foo', undefined]
'foo.png' => ['foo', 'png']
'foo.bar.png' => ['foo.bar', 'png']
'' => ['', undefined]
I find that to be what I want.