ZIP Code (US Postal Code) validation

I thought people would be working on little code projects together, but I don't see them, so here's an easy one:

Code that validates a valid US Zip Code. I know there are ZIP code databases out there, but there are still uses, like web pages, quick validation, and also the fact that zip codes keep getting issued, so you might want to use weak validation.

I wrote a little bit about zip codes in a side project on my wiki/blog:

https://benc.fogbugz.com/default.asp?W24

There is also a new, weird type of zip code.

https://benc.fogbugz.com/default.asp?W42

I can do the javascript code, but it would be interesting to see how many languages we can get here.

Solution 1:

Javascript Regex Literal:

US Zip Codes: /(^\d{5}$)|(^\d{5}-\d{4}$)/

var isValidZip = /(^\d{5}$)|(^\d{5}-\d{4}$)/.test("90210");

Some countries use Postal Codes, which would fail this pattern.

Solution 2:

function isValidUSZip(sZip) {
   return /^\d{5}(-\d{4})?$/.test(sZip);
}

Solution 3:

Here's a JavaScript function which validates a ZIP/postal code based on a country code. It allows somewhat liberal formatting. You could add cases for other countries as well. Note that the default case allows empty postal codes since not all countries use them.

function isValidPostalCode(postalCode, countryCode) {
    switch (countryCode) {
        case "US":
            postalCodeRegex = /^([0-9]{5})(?:[-\s]*([0-9]{4}))?$/;
            break;
        case "CA":
            postalCodeRegex = /^([A-Z][0-9][A-Z])\s*([0-9][A-Z][0-9])$/;
            break;
        default:
            postalCodeRegex = /^(?:[A-Z0-9]+([- ]?[A-Z0-9]+)*)?$/;
    }
    return postalCodeRegex.test(postalCode);
}

FYI The second link referring to vanity ZIP codes appears to have been an April Fool's joke.

Solution 4:

If you're doing for Canada remember that not all letters are valid

These letters are invalid: D, F, I, O, Q, or U And the letters W and Z are not used as the first letter. Also some people use an optional space after the 3rd character.

Here is a regular expression for Canadian postal code:

new RegExp(/^[abceghjklmnprstvxy][0-9][abceghjklmnprstvwxyz]\s?[0-9][abceghjklmnprstvwxyz][0-9]$/i)

The last i makes it case insensitive.