A substitution callback is a function that is called for each match found by a regex, and it returns the replacement string for that match. To replace only part of the found text in a regex, you can use substitution callbacks. Positive lookbehind is syntaxed like (
To remember the syntax for lookahead and lookbehinds I created a quick cheat sheet about it.Result = re. At
Using lookaheads, you can test strings against patterns without including them in the resulting match.
This exclusion can seem weird after working with regular expressions but when you think of it, that's the difference of lookaheads and groups. The interesting part for me is that it only matches Max and not the pattern defined in the lookahead ( (?= Mustermann)). This example matches Max whenever it is followed by a space and Mustermann otherwise it's not matching and returns null. use positive regex lookahead const regex = / Max(?= Mustermann) / Let's look at a typical example that you'll find when you read about lookaheads in JavaScript regular expressions. Regular expression lookaheads are not like captured groups
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