The onvrdisplaypresentchange property of the SpeechSynthesis interface represents an event handler that will run when the presenting state of a VR device changes — i.e. goes from presenting to not presenting, or vice versa (when the onvrdisplaypresentchange event fires).
The DeviceLightEvent provides web developers with information from photo sensors or similiar detectors about ambient light levels near the device. For example this may be useful to adjust the screen's brightness based on the current ambient light level in order to save energy or provide better readability.
The KeyboardEvent.code property represents a physical key on the keyboard (as opposed to the character generated by pressing the key). In other words, this property returns a value which isn't altered by keyboard layout or the state of the modifier keys.