PerformanceObserver
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.
Note: This feature is available in Web Workers.
The PerformanceObserver
interface is used to observe performance measurement events and be notified of new performance entries as they are recorded in the browser's performance timeline.
Constructor
PerformanceObserver()
-
Creates and returns a new
PerformanceObserver
object.
Static properties
PerformanceObserver.supportedEntryTypes
Read only-
Returns an array of the
entryType
values supported by the user agent.
Instance methods
PerformanceObserver.observe()
-
Specifies the set of entry types to observe. The performance observer's callback function will be invoked when performance entry is recorded for one of the specified
entryTypes
. PerformanceObserver.disconnect()
-
Stops the performance observer callback from receiving performance entries.
PerformanceObserver.takeRecords()
-
Returns the current list of performance entries stored in the performance observer, emptying it out.
Examples
Creating a PerformanceObserver
The following example creates a PerformanceObserver
watching for "mark" (PerformanceMark
) and "measure" (PerformanceMeasure
) events.
The perfObserver
callback provides a list
(PerformanceObserverEntryList
) which allows you to get observed performance entries.
function perfObserver(list, observer) {
list.getEntries().forEach((entry) => {
if (entry.entryType === "mark") {
console.log(`${entry.name}'s startTime: ${entry.startTime}`);
}
if (entry.entryType === "measure") {
console.log(`${entry.name}'s duration: ${entry.duration}`);
}
});
}
const observer = new PerformanceObserver(perfObserver);
observer.observe({ entryTypes: ["measure", "mark"] });
Specifications
Specification |
---|
Performance Timeline # dom-performanceobserver |
Browser compatibility
BCD tables only load in the browser