PerformanceObserverEntryList.getEntriesByType()

The getEntriesByType() method of the PerformanceObserverEntryList returns a list of explicitly observed performance entry objects for a given performance entry type. The list's members are determined by the set of entry types specified in the call to the observe() method. The list is available in the observer's callback function (as the first parameter in the callback).

This method is exposed to Window and Worker interfaces.

Syntax

entries = list.getEntriesByType(type);

Parameters

type

The type of entry to retrieve such as "frame". The valid entry types are listed in PerformanceEntry.entryType.

Return value

A list of explicitly observed PerformanceEntry objects that have the specified type. The items will be in chronological order based on the entries' startTime. If no objects have the specified type, or no argument is provided, an empty list is returned.

Example

function print_perf_entry(pe) {
  console.log("name: "        + pe.name      +
              "; entryType: " + pe.entryType +
              "; startTime: " + pe.startTime +
              "; duration: "  + pe.duration);
}
// Create observer for all performance event types
var observe_all = new PerformanceObserver(function(list, obs) {
  var perfEntries;
  // Print all entries
  perfEntries = list.getEntries();
  for (var i=0; i < perfEntries.length; i++) {
    print_perf_entry(perfEntries[i]);
  }
  // Print entries named "Begin" with type "mark"
  perfEntries = list.getEntriesByName("Begin", "mark");
  for (var i=0; i < perfEntries.length; i++) {
    print_perf_entry(perfEntries[i]);
  }
  // Print entries with type "mark"
  perfEntries = list.getEntriesByType("mark");
  for (var i=0; i < perfEntries.length; i++) {
    print_perf_entry(perfEntries[i]);
  }
});
// subscribe to all performance event types
observe_all.observe({entryTypes: ['frame', 'mark', 'measure', 'navigation', 'resource', 'server']});
var observe_frame = new PerformanceObserver(function(list, obs) {
  var perfEntries = list.getEntries();
  // Should only have 'frame' entries
  for (var i=0; i < perfEntries.length; i++) {
    print_perf_entry(perfEntries[i]);
  }
});
// subscribe to only the 'frame' event
observe_frame.observe({entryTypes: ['frame']});

Specifications

Browser compatibility

[1] Only activated in Nightly builds. Controlled by the dom.enable_performance_observer preference.