call a function from within custom button fullcalendar vue

1data: function() {
2    return {    
3        calendarOptions: {
4            headerToolbar: {
5                right: "today prev,next",
6                center: "title",
7                left: "dayGridMonth,timeGridWeek,timeGridDay",
8            },
9            customButtons: {
10                next: {
11                    click: this.nextButton,
12                },
13                prev: {
14                    click: this.prevButton,
15                },
16            },
17        },
18    };
19},
20methods: {
21    nextButton: function(event) {
22        console.log(event);
23        // calendar.next();
24    },
25
26    prevButton: function(event) {
27        console.log(event);
28        // calendar.prev();
29    },
30}