等待Bootbox确认运行Ajax

我的代码是,

$('#change_pass_form').submit(function () {
    bootbox.confirm({
        message: "Your password is about to be changed. Are you sure?",
        buttons: {
            cancel: {label: '<i class="fa fa-times"></i> Cancel'},
            confirm: {label: '<i class="fa fa-check"></i> Confirm'}
        },
        callback: function (result) {
            if (result === 'true') {
                $.ajax({
                    type: 'POST',
                    url: 'php_files/profile_php_files/profile_password_change_process.php',
                    data: {
                        user_id: sessionStorage.getItem('user_id'),
                        new_password: $('#new_password').val(),
                        repeat_password: $('#repeat_password').val()
                    },
                    success: function (data) {
                        if (data === 'correct') {
                            bootbox.alert({
                                size: 'small',
                                message: 'Your password has been changed. You will now be logged out.',
                                callback: function () {
                                    window.location.replace('index.html');
                                }
                            });
                            return true;
                        } else {
                            bootbox.alert({
                                size: 'small',
                                message: data
                            });
                            return false;
                        }
                    }
                });
            } else {
                return false;
            }
        }
    });
});