Regex to count the number of capturing groups in a regex

Question

I need a regex that examines arbitrary regex (as a string), returning the number of capturing groups. So far I have...

arbitrary_regex.toString().match(/\\((         


        

Answer 1

Modify your regex so that it will match an empty string, then match an empty string and see how many groups it returns:

var num_groups = (new RegExp(regex.toString() + '|')).exec('').length - 1;

Example: http://jsfiddle.net/EEn6G/