(function($) {
    $(document).ready(function() {
            // Selecting box
        var $FindCandidateBox = $("div.boxy.single.venstreFindCandidate");

            // Selecting form, so we can return false to submit; if value isn't true
        var $FindCandidateForm = $("div.boxy.single.venstreFindCandidate form");

            // Select input field, so we got the value
        var $FindCandidateInput = $("div.inputFindCandidate input", $FindCandidateForm);

            // Hook on form, so we control it
        $FindCandidateForm.submit(function() {
                // Regular Expression 3-4 integers is allowed!
            var regExpr = new RegExp('^[0-9]{4}$');
                // Test our regular expression
            if (!regExpr.test($FindCandidateInput.val())) {
                    // Case of error
                $FindCandidateBox.addClass('error')
                $("div.label", $FindCandidateForm).html("<strong>Der skete en fejl:</strong><br />Indtast venligst et postnumre med 4 cifre.<br /><br />");
                return false;
            }

            return true;
        });
    });
})(jQuery);