function changePassword() {
        if (isInputEmpty()) {
            $.ajax({
                type: 'POST',
                data: '...'
                url: '...',
                success: function (result) {
                    if (result.substring(0, 3) != "!!!") {
                        //success
                    } else {
                        //faliure
                    }
                },
                error: function () {
                    }
            });
        }
    }

And of course,in production, it always reported success and never changed the password, because of equally bad server code.

By You will be proud of our code!, 2017-12-15 11:30:02