Returns the current time as defined by performance.now if available, and Date.now if not.
The current time is updated at the start of a frame; it is thus consistent during the frame, and any timers scheduled during the same frame will be synchronized.
If this method is called outside of a frame, such as in response to a user event, the current time is calculated and then fixed until the next frame,
again ensuring consistent timing during event handling.
Returns the current time as defined by performance.now if available, and Date.now if not. The current time is updated at the start of a frame; it is thus consistent during the frame, and any timers scheduled during the same frame will be synchronized. If this method is called outside of a frame, such as in response to a user event, the current time is calculated and then fixed until the next frame, again ensuring consistent timing during event handling.