The observe()
method of the PerformanceObserver
interface is used to specify the set of performance entry types to observe.
The performance entry types are specified as an array of string objects, each naming one entry type; the type names are documented in Performance entry type names in PerformanceEntry.entryType.
When a matching performance entry is recorded, the performance observer's callback function—set when creating the PerformanceObserver
—is invoked.
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++) {
}
});
observer.observe({entryTypes: ["mark", "frame"]});
function perf_observer(list, observer) {
}
var observer2 = new PerformanceObserver(perf_observer);
observer2.observe({entryTypes: ["measure"]});