function test(data, callback) {
    if(data !== null) {
        if(typeof callback == 'function') {
            callback.success();
        }
    } else {
        if(typeof callback == 'function') {
            callback.error();
        }
    }
}

test($(form).serialize(), function () {
    success: function () {
    },
    error: function () {
    }
});