PerformanceNavigationTiming: unloadEventEnd property

{{APIRef("Performance API")}}

The unloadEventEnd read-only property returns a {{domxref("DOMHighResTimeStamp")}} representing the time immediately after the previous document's unload event handler completes.

Value

The unloadEventEnd property can have the following values:

• A {{domxref("DOMHighResTimeStamp")}} representing the time immediately after the previous document's unload event handler completes.
• 0 if there is no previous document.
• 0 if the previous page was on another origin.

Examples

Measuring unload event handler time

The unloadEventEnd property can be used to measure how long it takes to process the unload event handler.

This is useful to measure the time of long running unload event handlers.

window.addEventListener("unload", (event) => {
  // Some long running code
});

Example using a {{domxref("PerformanceObserver")}}, which notifies of new navigation performance entries as they are recorded in the browser's performance timeline. Use the buffered option to access entries from before the observer creation.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    const unloadEventTime = entry.unloadEventEnd - entry.unloadEventStart;
    if (unloadEventTime > 0) {
      console.log(
        `${entry.name}: unload event handler time: ${unloadEventTime}ms`,
      );
    }
  });
});

observer.observe({ type: "navigation", buffered: true });

Example using {{domxref("Performance.getEntriesByType()")}}, which only shows navigation performance entries present in the browser's performance timeline at the time you call this method:

const entries = performance.getEntriesByType("navigation");
entries.forEach((entry) => {
  const unloadEventTime = entry.unloadEventEnd - entry.unloadEventStart;
  if (unloadEventTime > 0) {
    console.log(`${entry.name}:
      load event handler time: ${unloadEventTime}ms`);
  }
});

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• unload event