PerformanceObserver.observe()

options

A PerformanceObserverInit dictionary with the following possible members:

entryTypes

An array of string objects, each specifying one performance entry type to observe. May not be used together with the "type" or "buffered" options.

type

A single string specifying exactly one performance entry type to observe. May not be used together with the entryTypes option.

buffered

A boolean flag to indicate whether buffered entries should be queued into the observer's buffer. Must be used only with the "type" option.

See PerformanceEntry.entryType for a list of valid performance entry type names. Unrecognized types are ignored, though the browser may output a warning message to the console to help developers debug their code. If no valid types are found, observe() has no effect.

None (undefined).

This example creates and configures two PerformanceObservers; one watches for "mark" and "frame" events, and the other watches for "measure" events.

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"]});