Question

How can I include a dynamic variable into a regexp object?

var pattern:RegExp = new RegExp(/'a '/ + keyword, '/gi');

In this case, I’d like the regex to match “a bird”, or “A biRD” (if ‘bird’ is the keyword). However, ‘bird’ should not match if it is on its own.

Furthermore, I have a follow up question (I hope it’s not too much to ask!):
How would I do the exact thing above, but in which the regex only matches if the keyword is NOT preceded by ‘a ‘ (I believe this involves the use of the ^ or the !, but I can’t seem to find any clear documentation in any language for my specific request).

In the case of my second question test cases would look like this:

WORKS

abird
bird
bbbbirdddd

DOESN’T WORK

a bird
a birdddd

Any help will be greatly appreciated!

Answer 1

ActionScript 3.0 supports lookbehinds and the case-insensitive modifier:

/(?<=a\s+)bird/i

See here for more information on how to construct a regular expression from a variable: Using a Variable in an AS3, Regexp.

For the second part of your question:

/(?<!a\s+)bird/i