The EventCounts interface of the Performance API provides the number of events that have been dispatched for each event type.

An EventCounts instance is a read-only Map-like object, in which each key is the name string for an event type, and the corresponding value is an integer indicating the number of events that have been dispatched for that event type.

This interface has no constructor. You typically get an instance of this object using the performance.eventCounts property.

size

See Map.prototype.size for details.

entries()

See Map.prototype.entries() for details.

forEach()

See Map.prototype.forEach() for details.

get()

See Map.prototype.get() for details.

has()

See Map.prototype.has() for details.

keys()

See Map.prototype.keys() for details.

values()

See Map.prototype.values() for details.

Below are a few examples to get information from an EventCounts map. Note that the map is read-only and the clear(), delete(), and set() methods aren't available.

for (entry of performance.eventCounts.entries()) {
  const type = entry[0];
  const count = entry[1];
}

const clickCount = performance.eventCounts.get("click");

const isExposed = performance.eventCounts.has("mousemove");
const exposedEventsCount = performance.eventCounts.size;
const exposedEventsList = [...performance.eventCounts.keys()];

• performance.eventCounts
• PerformanceEventTiming
• Map