为什么此代码有效？

Question

Just wondering why this code is working:

    var response = $.ajax({
            data: {'my data here'},
            url: 'myurl.php',
            type: 'POST',
            dataType: 'JSON'
        });

        response.done(success_callback_here,
                // watch this below:
                // this snippet will execute if myurl.php echo something.
                // otherwise, it doesn't
                function () {
                    removeOverLayer();
                }
        );
        response.always('always_fun_here');
        response.fail(......);

I've tried to find something useful from here, but I didn't get much from it. Can someone tell me why please?

Answer 1

If you look in the jquery documentation

you can see that you can add a second callback (or array of) function(s) to your done() function as a param