File regex in npm replace

Question

I'm trying to match the following file formats to prefix the files with an absolute URL. The strings are part of an index.html file and I'm using npm replace to find/replace. Here are the different file names:

favicon.ico
main.somestringwithcharacterandletters.css
main.somestringwithcharacterandletters.js
somestringwithcharactersandletters.woff
somestringwithcharactersandletter.ttf

I've tried the following regex:

(main\.)?(\w)+\.(css|js|woff|woff2|eot|ttf|png|ico){1}

This matches the last character in the filename and the extension instead of the full filename and the extension. What needs to be changed to match the full filename so I can prefix an absolute path?

Note that {1} is never ever useful in regex. A quantifier of 1 occurrence is the same as no quantifier — Aaron
– Aaron, Commented Jul 26, 2016 at 15:07
(\w)+ -> (\w+). Instead of quantifying a group that captures the last matched value, you should quantify the pattern inside the group. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 26, 2016 at 15:10
Add a $ at the end to indicate that it should match the end part of the name no matter what intervening folders are called? — Mad Physicist
– Mad Physicist, Commented Jul 26, 2016 at 15:10
Not my issue. As you see from that regex101 it is working for me. I haven't tried it with npm replace. I can see your suggestion is more logical. — Bryce Drew
– Bryce Drew, Commented Jul 26, 2016 at 17:16

Wiktor Stribiżew · Accepted Answer · 2016-07-26 18:16:22Z

1

Remove the redundant {1} and what is more important - move the + into the second capture group:

(main\.)?(\w+)\.(css|js|woff2?|eot|ttf|png|ico)
            ^                                  ^

See the regex demo.

When you set a quantifier to a group, the whole group pattern is matches repeatedly, but the contents of the group stack is constantly re-written with each subsequent match. Thus, always check what you quantify, in many situations, you want to quantify the group pattern, not the group itself (unless it is a non-capturing group, when you know nothing is captured and we use it to just group a sequence of subpatterns).

answered Jul 26, 2016 at 18:16

Wiktor Stribiżew

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