PerformanceResourceTiming.workerStart

The workerStart read-only property of the PerformanceResourceTiming interface returns a DOMHighResTimeStamp immediately before dispatching the FetchEvent if a Service Worker thread is already running, or immediately before starting the Service Worker thread if it is not already running. If the resource is not intercepted by a Service Worker the property will always return 0.

Note: This feature is available in Web Workers.

Syntax

resource.workerStart;

Value

A DOMHighResTimeStamp.

Example

In the following example, the value of the *Start and *End properties of all "resource" type events are logged.

function print_PerformanceEntries() {
  // Use getEntriesByType() to just get the "resource" events
  var p = performance.getEntriesByType("resource");
  for (var i=0; i < p.length; i++) {
    print_start_and_end_properties(p[i]);
  }
}
function print_start_and_end_properties(perfEntry) {
  // Print timestamps of the PerformanceEntry *start and *end properties 
  properties = ["connectStart", "connectEnd",
                "domainLookupStart", "domainLookupEnd",
                "fetchStart", 
                "redirectStart", "redirectEnd",
                "requestStart", 
                "responseStart", "responseEnd",
                "secureConnectionStart",
		"workerStart"];

  for (var i=0; i < properties.length; i++) {
    // check each property
    var supported = properties[i] in perfEntry;
    if (supported) {
      var value = perfEntry[properties[i]];
      console.log("... " + properties[i] + " = " + value);
    } else {
      console.log("... " + properties[i] + " = NOT supported");
    }
  }
}

Specifications

Specification Status Comment
Resource Timing Level 1
The definition of 'workerStart' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support431658 No3211
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support4343 Yes5832114.0

Document Tags and Contributors

Contributors to this page: ExE-Boss, chrisdavidmills, libbymc, rolfedh, AFBarstow
Last updated by: ExE-Boss,