```js function (event) { // return true to take into account, false to ignore } ``` </td> </tr> </table> ### headerToolbar - Type `object` or `function` - Default `{start: 'title', center: '', end: 'today prev,next'}` > Views override the default value as follows: > - dayGridDay `{start: 'title', center: '', end: 'today prev,next'}` > - dayGridMonth `{start: 'title', center: '', end: 'today prev,next'}` > - dayGridWeek `{start: 'title', center: '', end: 'today prev,next'}` > - listDay `{start: 'title', center: '', end: 'today prev,next'}` > - listMonth `{start: 'title', center: '', end: 'today prev,next'}` > - listWeek `{start: 'title', center: '', end: 'today prev,next'}` > - listYear `{start: 'title', center: '', end: 'today prev,next'}` > - resourceTimelineDay `{start: 'title', center: '', end: 'today prev,next'}` > - resourceTimelineMonth `{start: 'title',