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May 16The Validation Regex
by in Representative Line on 2016-06-30Regular expressions are a powerful tool for validating inputs, but what if your input is itself a regular expression? Is there a regular expression that can validate regular expressions?
Well, yes, if your regular expression engine supports recursion: /^((?:(?:[^?+*{}()[\]\\|]+|\\.|\[(?:\^?\\.|\^[^\\]|[^\\^])(?:[^\]\\]+|\\.)*\]|\((?:\?[:=!]|\?<[=!]|\?>)?(?1)??\)|\(\?(?:R|[+-]?\d+)\))(?:(?:[?+*]|\{\d+(?:,\d*)?\})[?+]?)?|\|)*)$/.