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
CodePudding user response：
If you really want to use regex, I would suggest to use two regex:
// example with 'foo.baz.bing.bong'
const firstString = /^. (?=\.\w )./g // match 'foo.baz.bing.'
const secondString = /\w $/g // match 'bong'CodePudding user response：
For the first capture group, you could start the match with 1 or more word characters. Then optionally repeat a . and again 1 or more word characters.
Then you can use an optional non capture group matching a . and capturing 1 or more word characters in group 2.
As the second non capture group is optional, the first repetition should be on greedy.
^(\w (?:\.\w )*?)(?:\.(\w ))?$
The pattern matches
^Start of string(Capture group 1\w (?:\.\w )*?Match 1 word characters, and optionally repeat.and 1 word characters
)Close group 1(?:Non capture group to match as a whole\.(\w )Match a.and capture 1 word chars in capture group 2
)?Close non capture group and make it optional$End of string