如何不使用^和Capture组使用正则表达式？

Question

How do I use the Not operator ^ with the capture groups in regex.

Example: I have two URLs coming in http://api.example.com and http://example.com

How would I make a capture group on all URLs that do not contain api .

How I thought this would look is var notAPI = /(^api)/;

Answer 1

Regex only has negative lookaheads and lookbehinds. Their spirit is: you only look, you don't move forward.

This is a negative lookahead:

(?!nomatch)

And this is a negative lookbehind:

(?<!nomatch)

You can incorporate these lookarounds into your regex like this:

var notAPI = /^((?!api).)*$/;

Take a look at this answer - it also explains how it works.