Why This Regex Does Split Second Double Quote But Not First Double Quote?

I have this regex: let regex = /(?=\.|[\'])/; test = '\'test.test\'' test.split(regex) which outputs: [''test', '.test', '''] whereas I want [''', 'test', '.test', '''] I can't

Solution 1:

This is not pure regex solution but you may use this regex with a capture group and filter empty results:

const str = '"test.test"';

var arr = str.split(/(")|(?=\.)/).filter(Boolean)

console.log(arr)

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Issue with your approach:

Your regex is using a lookahead assertion that can be shortened to:

(?=[."])

Which means match a zero width match that has either a dot or " at immediate next position.

Since your input has " at the start it matches position 0, then position before dot and finally position before last closing " (total 3 matches).