Web/API/PerformanceObserver/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.

Syntax

var observer = new PerformanceObserver(callback);

Parameters

callback: A PerformanceObserverCallback callback that will be invoked when observed performance events are recorded. When the callback is invoked, its first parameter is a list of performance observer entries and the second parameter is the observer object.

Return value

A new PerformanceObserver object which will call the specified callback when observed performance events occur.

Example

var observer = new PerformanceObserver(function(list, obj) {
  var entries = list.getEntries();
  for (var i=0; i < entries.length; i++) {
    // Process "mark" and "frame" events
  }
});
observer.observe({entryTypes: ["mark", "frame"]});

function perf_observer(list, observer) {
  // Process the "measure" event 
}
var observer2 = new PerformanceObserver(perf_observer);
observer2.observe({entryTypes: ["measure"]});

Specifications

Specification	Status	Comment
Performance Timeline Level 2The definition of 'PerformanceObserver()' in that specification.	Candidate Recommendation	Initial definition of `PerformanceObserver()` constructor.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`PerformanceObserver()` constructor	Chrome Full support 52	Edge Full support ≤79	Firefox Full support 57	IE No support No	Opera Full support 39	Safari Full support 11	WebView Android Full support 52	Chrome Android Full support 52	Firefox Android Full support 57	Opera Android Full support 41	Safari iOS Full support 11	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
No support: No support

PerformanceObserver() by Mozilla Contributors is licensed under CC-BY-SA 2.5.