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javascriptregexregex-lookarounds

Why doesn't positive lookahead work as first capture group?

I'm using the following regex;

((?:_missing_:|_exists_:)[a-z0-9]+)|(([a-z0-9]+)(?=:))

To match a lucene query string;

_missing_:title age:(>=10 AND < 20) AND age:123 AND _exists_:title123

The first non-capture group is not respected and returns _missing_:title and not title. Using a positive lookahead makes the entire regex fail to match anything.

It should return the following array;

['title', 'age', 'age', 'title123']
Solution

  • Change your regex like below and then grab the strings you want from group index 1 and 2.

    (?:_missing_:|_exists_:)([a-z1-9]+)|([a-z1-9]+)(?=:)

    You don't need to include the non-capturing group (?:_missing_:|_exists_:) inside a capturing group. This is the reason for returning missing:title instead of title . And also Capturing group for [a-z1-9]+ would be enough.

    DEMO