# onBeforeViewChange

### Description

@short: Fires before the user changes the current view to some other one

@signature: onBeforeViewChange: (old_mode: string, old_date: object, mode: string, date: object) =\> boolean

### Parameters

- `old_mode` - (required) *string* - the currently active view
- `old_date` - (required) *object* - the currently active date
- `mode` - (required) *string* - the new view
- `date` - (required) *object* - the new date

### Returns
- ` result` - (boolean) - defines whether the default action of the event will be triggered (<b>true</b>) or canceled (<b>false</b>)

### Example

~~~jsx
scheduler.attachEvent("onBeforeViewChange", function(old_mode,old_date,mode,date){
    //any custom logic here
    return true;
});
~~~

### Related samples
- [Configuring the Map view](https://docs.dhtmlx.com/scheduler/samples/03_extensions/23_map_view_timeframes.html)

### Details

- The event is blockable. Return *false* and the scheduler will leave the current view opened.
- The event also fires when the scheduler is initially being rendered on the page. In this case, the **old_mode** and **old_date** parameters are underfined.