Baseline Widely available
Note: This feature is available in Web Workers.
The read-only startTime property returns the first timestamp recorded for this PerformanceEntry. The meaning of this property depends on the value of this entry's entryType.
A DOMHighResTimeStamp representing the first timestamp when the PerformanceEntry was created.
The meaning of this property depends on the value of this performance entry's entryType:
element
Either the value of this entry's renderTime if it is not 0, otherwise the value of this entry's loadTime.
event
The time the event was created, i.e., the event's timeStamp property.
first-input
The time the first input event was created, i.e., that event's timeStamp.
largest-contentful-paint
The value of this entry's renderTime if it is not 0, otherwise the value of this entry's loadTime.
layout-shift
The time when the layout shift started.
longtask
The time when the task started.
mark
The time at which the mark was created by a call to performance.mark().
measure
The time at which the measure was created by a call to performance.measure().
navigation
Always 0.
paint
The time when the paint occurred.
resource
The value of this entry's fetchStart property.
taskattribution
Always 0.
visibility-state
The time when the visibility state change occurred.
The following example shows the use of the startTime property which you can log during performance observation.
Note: The performance.mark() method allows you to set your own startTime, and the performance.measure() method allows to set the start of the measure.
performance.mark("my-mark");
performance.mark("my-other-mark", { startTime: 12.5 });
loginButton.addEventListener("click", (clickEvent) => {
performance.measure("login-click", { start: clickEvent.timeStamp });
});
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"] });
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