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PerformanceNavigationTiming.unloadEventStart

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This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The unloadEventStart 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.

This property is Read only .

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 Status Comment
Navigation Timing Level 2
The definition of 'unloadEventStart' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support. No support No support No support No support No support
Feature Android Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support. No support No support No support No support No support No support

Document Tags and Contributors

 Contributors to this page: rolfedh, AFBarstow
 Last updated by: rolfedh,