A regular expression that matches strings that don't start with a set of words

Question

I have a regular expression that matches strings that start with either the word "db" or the word "admin":

/^\/(db|admin)\//

I'm refactoring my code and my requirements have changed: Now I need the opposite, i.e. a regular expression that matches strings that don't start with one of those two words. Is this possible with regular expressions?

Note: I cannot use JS API - the regular expression is inserted in Express.js's app.all(path, callback) method directly (as the path).

you just want a true/false test (using the full string after testing)? — GitaarLAB, Aug 30 '14 at 14:54
@GitaarLAB Yes, it's just a true/false test. the strings are HTTP request paths, and the regular expression should match all paths except those that start with either "/db/" or "/admin/". — Šime Vidas, Aug 30 '14 at 14:55
Yes I think I agree that the `(?!)` look-ahead in that linked possible duplicate would work here. — Pointy, Aug 30 '14 at 14:57
@GitaarLAB I have to provide a regular expression, and then Express.js uses it on the request paths to perform the test. — Šime Vidas, Aug 30 '14 at 14:59

score 4 · Answer 1 · answered Aug 30 '14 at 15:07

4

Thanks to Nico for pointing out that JavaScript RegExp has (?!) functionality. The solution seems to be:

/^\/(?!admin|db)/

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answered Aug 30 '14 at 15:07

Šime Vidas

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Do you perhaps want to include the `/` inside the lookahead? Like, `/^\/(?!(?:admin|db)\/)/`? That way you'd allow "/administrator/" (which may or may not be important to you). – Pointy Aug 30 '14 at 15:14
@Pointy Yes, this is a slight improvement :) (With this, I will also catch "/admin" or "/db" but those paths don't make sense anyway.) – Šime Vidas Aug 30 '14 at 15:23

A regular expression that matches strings that don't start with a set of words

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