Download - The Bastards Book of Regular Expressions

Changing phone format (TODO) 141Replace (\1)-\2-\3This pattern does the job of matching an optional 1 as well as an optional hyphen or whitespacebefore the actual ten digits of the phone number. We can use the same value for the Replace fieldbecause we’re using the same captured groups.If you apply it to the following numbers:55561640401 555 29290102 555 616 4040The resulting transformation is:(555)-616-4040(555)-292-90102 555 616 4040The last number is not transformed because its prefix is a 2, which is something we don’t expect (ina standard U.S. number).A more precise groupingThere’s something a bit off to the previous solution. Since both the 1 and the whitespace/hyphenare optional, that means our regex would also match the following:-555-212-0000And turn it into:(555)-212-0000You might think: Yeah, so? Well, it’s true that there’s probably no harm done in matching (and thenignoring) a stray hyphen, sometimes you have to ask, why is there a stray hyphen without a 1? Itmay be harmless to us, but it might indicate that the user misunderstood what was supposed to bethe phone field. Perhaps they’re trying to enter an international format and got cutoff.Who knows. But just to be safe, let’s make our regex more rigid so that it won’t match that kind ofinput. In other words, we want a regex that matches: