Question

I’m working on a simple form that I need to validate against UK postcodes. No problem there but I need to validate depending on the character length. The user can input only the first half of a postcode (i.e. SW1) or a full postcode (i.e. SW1 1AB).

I thought the best approach would be to check the length on KeyPress and validate against RegEx for either half a postcode or the whole thing. See below:

jQuery('.ValPostCode').keyup(
    function(){

        if (jQuery(this).length < 5){
            jQuery.validator.addMethod("ValPostCode", function(value, element) {
                return this.optional(element) || /([A-PR-UWYZa-pr-uwyz]([0-9]{1,2}|([A-HK-Ya-hk-y][0-9]|[A-HK-Ya-hk-y][0-9]([0-9]|[ABEHMNPRV-Yabehmnprv-y]))|[0-9][A-HJKS-UWa-hjks-uw]))/.test(value);
            }, "Please enter a valid postcode");                            
        } else if (jQuery('.ValPostCode').length > 4) {
             jQuery.validator.addMethod("ValPostCode", function(value, element) {
            return this.optional(element) || /^(GIR\\s{0,1}0AA|[A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKS-UW])\\s{0,1}[0-9][ABD-HJLNP-UW-Z]{2})$/.test(value);
            }, "Please enter a valid postcode");
        }

    });

So, if the char length of .ValPostCode is less than 5 it validates only for the first half of a UK postcode, else it checks for a full and valid UK postcode.

At one point I was outputting the length of .ValPostCode but it always stopped at 1 (first keypress) and then didn’t carry on any further (i.e. wouldn’t count up with subsequent keypresses).

I hope I’ve explained myself clearly enough, please let me know if I’m not being clear.

I’ve searched for similar problems to try and fix this for myself but I couldn’t find anything. Any help appreciated!

Answer 1

The length of $(selector).length (or jQuery(selector).length) will always be the number of elements on the screen that match the given selector. Try using $(selector).val().length to get the value of a form element and check its lenght instead.