PerformanceNavigationTiming.unloadEventStart

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The unloadEventStart read-only property returns a timestamp representing the time value equal to the time immediately before the user agent starts the unload event of the previous document. If there is no previous document, this property returns 0.

Syntax

perfEntry.unloadEventStart;

Return Value

A timestamp representing the time value equal to the time immediately before the user agent starts the unload event of the previous document.

Example

The following example illustrates this property's usage.

function print_nav_timing_data() {
  // Use getEntriesByType() to just get the "navigation" events
  var perfEntries = performance.getEntriesByType("navigation");

  for (var i=0; i < perfEntries.length; i++) {
    console.log("= Navigation entry[" + i + "]");
    var p = perfEntries[i];
    // dom Properties
    console.log("DOM content loaded = " + (p.domContentLoadedEventEnd - p.domContentLoadedEventStart));
    console.log("DOM complete = " + p.domComplete);
    console.log("DOM interactive = " + p.interactive);

    // document load and unload time
    console.log("document load = " + (p.loadEventEnd - p.loadEventStart));
    console.log("document unload = " + (p.unloadEventEnd - p.unloadEventStart));

    // other properties
    console.log("type = " + p.type);
    console.log("redirectCount = " + p.redirectCount);
  }
}

Specifications

Specification
Navigation Timing Level 2 # dom-performancenavigationtiming-unloadeventstart

Browser compatibility

BCD tables only load in the browser