RegExp lookbehind assertions would be useful to me. Especially with Safari support in iOS 16.4.
My use case is wanting to match on a full word (not just part of a word), so the proceeding character must be the start of the string, a whitespace or newline, or a period or comma. However, preferably I would not capture what proceeds the first word as this is not important to me.
// EX 1: Colder with a low of 5.
// EX 2: a low of 5 below zero.
// EX 3: high of 5. low of 6.
let lowRegex = /(?<=^|\s|\.|\,)low of (\d+|zero)( below zero)?/
Without the lookbehind assertion I would capture low zero in below zero from example 2 which was not what I was intending. Alternatively if I just decide to capture the first character then my matches would often be prefixed by a whitespace/newline or period/comma which I'd rather ignore, especially if I intend on replacing the match in the original string.