Custom boundary - not included in the match.

[anboanbo]

I have this one to match upper case work 3-6 chars long that ends with
blankspace :
[A-Z]{3,6}(?= )

Is what i need becuase the blankspace is not included.

But how do i change it so that it also check if there is a blank space
infront ?

Also i dont really understand the (?= ) thing, what is the meaning of
= in regular expresions ?

(I work in javascript).

Best regards.