Question

What would be the easiest way to allow only letters/numbers in a textbox. We are using JS/jQuery, but don’t want to use a validation plugin?

Answer 1

You can use a simple regex on form submit to evaluate the contents of the text box, show an error, and stop the form submit. Make a function out of the check and you can also apply it when the text box loses focus. Do this very often and you’ll find that you’ve reimplemented the validation plugin.

$(function() {
    $('form').submit( function() {
        return validateTB( $('#textbox'), true, $('#textboxError') );
    });

    $('#textbox').blur( function() {
        validateTB( $(this), true, $('#textboxError') );
    });

    function validateTB(tb,required,msg) {
        var $tb = $(tb);
        var re = '/^[a-z0-9]';
        if (required) {
           re += '+';
        }
        else {
           re += '*';
        }
        re += '$/';

        if ($tb.val().match(re) == null) {
           $(msg).show();
           return false;
        }
        $(msg).hide();
        return true;
    }
});