How to check for duplicate word with REGEX

I have a following string:

var string = "(one)(two)(one)(five)";

I would like to know how can I check that for duplicates with REGEX. It is supposed to return a Boolean value. For my example, it should return true.

Thank you!

>Solution :

You can use backreferences to accomplish this.

\1 through \9 Substituted with the text matched between the 1st through 9th numbered capturing group.

Therefore, something like this should do the trick:


This works by capturing the text in your first parentheses block, and then looking to see if that same text appears in any other parentheses.

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