PerformanceObserver()

The PerformanceObserver() constructor creates a new PerformanceObserver object with the given observer callback. The observer callback is invoked when performance entry events are recorded for the entry types that have been registered, via the observe() method.

Inputs: callback A PerformanceObserverCallback callback that will be invoked when observed performance events are recorded. When the callback is invoked, the following parameters are available: entries The list of performance observer entries. observer The observer object that is receiving the above entries. options An object with the following properties: droppedEntriesCount The number of entries which could not be recorded because the Performance object’s internal buffer was full.