javascript regex lookahead why abc match?-CodePudding

Input text is:

test 
abc abc

I want to get all text before abc with

. (?=abc)

https://regex101.com/r/4XiJ2r/1

why with 2 abc it matches the first one?

CodePudding user response：

Adding a ? (to make it . ?(?=abc)) to your quantifier will make it lazy, so it'll stop at the first ocurrence, but it will still find the other ocurrences and put them in different "groups": https://regex101.com/r/BjrowX/1

CodePudding user response：

The quantifier requires the match to be at least 1 character. In abc abc there's nothing before the first abc, so it can't be the match. So the match is everything before the second abc.

CodePudding user response：

You need to handle new lines, so you need m flag. You don't need global search, because you need to stop capturing before first abc appearance, so remove g flag. This is one of the multiple options:

const str = `test
abc abc`;

const result = str.match(/[\s\S]*?(?=abc)/m);

console.log(result);