Lookarounds are zero-width assertions that match a string without consuming anything. ECMAScript has lookahead assertions that does this in forward direction, but the language is missing a way to do this backward which the lookbehind assertions provide. With lookbehind assertions, one can make sure that a pattern is or isn't preceded by another, e.g. matching a dollar amount without capturing the dollar sign.
Specification currently under development in a Working Group
Status in Chromium
Enabled by default
Consensus & Standardization
Search tagsregexp, regular expressions,
Last updated on 2020-11-09