Submit Form Via Ajax if Ketchup Validates

$('#contact-form').submit(function(e) {

    //if ketchup validates
    if( $('#contact-form').ketchup("isValid") ) {

        //serialize the form data and add an ajax variable
        formData = $(this).serialize() + '&ajax=1';

        //send the form via ajax
        $.post($('#contact-form').attr('action'),formData, function(response){
            if(response=='1') {
                //do some stuff here
                console.log('success');
            } else {
                //got some erros
                var json = jQuery.parseJSON(response);
                console.log(response);
            }
        });
    }

    //don't submit normally
    return false;

});