JavaScript Regexp_lookahead Guide
Lookahead and lookbehind assertions match positions based on surrounding patterns without consuming characters. The guide walks through Lookahead/Lookbehind. Positive lookahead: `x(?=y)` — match x only if followed by y. Negative: `x(?!y)` — match x only if NOT followed by y. Positive lookbehind: `(?<=y)x` — match x only if preceded by y. Negative: `(?Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.