Javascript UK Postcode Validation [duplicate]

Question

Possible Duplicate:
UK Postcode Regex (Comprehensive)

I have the following code for validating postcodes in javascript:

function valid_postcode(postcode) {
    postcode = postcode.replace(/\s/g, "");
    var regex = /[A-Z]{1,2}[0-9]{1,2} ?[0-9][A-Z]{2}/i;
    return regex.test(postcode);
}

Tests:

CF47 0HW - Passes - Correct
CF47 OHW - Passes - Incorrect

I have done a ton of research but can't seem to find the definitive regex for this common validation requirement. Could someone point me in the right direction please?

Answer 1

Make your regex stricter by adding ^ and $. This should work:

function valid_postcode(postcode) {
    postcode = postcode.replace(/\s/g, "");
    var regex = /^[A-Z]{1,2}[0-9]{1,2} ?[0-9][A-Z]{2}$/i;
    return regex.test(postcode);
}

Answer 2

You want a 'definitive regex' - given all the permutations of the UK postcodes, it needs to be therefore 'unnecessarily large'. Here's one I've used in the past

"(GIR 0AA)|((([ABCDEFGHIJKLMNOPRSTUWYZ][0-9][0-9]?)|(([ABCDEFGHIJKLMNOPRSTUWYZ][ABCDEFGHKLMNOPQRSTUVWXY][0-9][0-9]?)|(([ABCDEFGHIJKLMNOPRSTUWYZ][0-9][ABCDEFGHJKSTUW])|([ABCDEFGHIJKLMNOPRSTUWYZ][ABCDEFGHKLMNOPQRSTUVWXY][0-9][ABEHMNPRVWXY])))) [0-9][ABDEFGHJLNPQRSTUWXYZ]{2})"

Notice I never just use A-Z, for instance, because in each part there are always certain letters excluded.