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There are times when you may want to use the 9 digit zip code validation for US. The 9 digit zip code is usually in format like this #####-####. For a 9 digit US zip code validation use below regular Expression. ^([0-9]{5}-[0-9]{4})$.
Front end validation. On the front end, we're already doing the best we can to help the proper entry of a zip code through HTML5 input attributes pattern, maxlength, and required. <input type=text pattern=[0-9]* maxlength=5 required name=zip id=zip>. Notice it's not of type number.