Useful Javascript Regex Link

(?:x) Matches x but does not capture it. In other words, no numbered references are created for the items within the parenthesis. /(?:.d){2}/ matches but doesn’t capture “cdad”.

x(?=y) Positive lookahead: Matches x only if it’s followed by y. Note that y is not included as part of the match, acting only as a required conditon. /George(?= Bush)/ matches “George” in “George Bush” but not “George Michael” or “George Orwell”. /Java(?=Script|Hut)/ matches “Java” in “JavaScript” or “JavaHut” but not “JavaLand”.

x(?!y) Negative lookahead: Matches x only if it’s NOT followed by y. Note that y is not included as part of the match, acting only as a required condiiton. /^\d+(?! years)/ matches “5” in “5 days” or “5 oranges”, but not “5 years”.

via JavaScript Kit- RegExp (regular expression) object.