resource-timing-api.js

(function() {
  /**
   * Creates array of timing entries from Resource Timing Interface
   */
  function getTimings() {
    var entries = [];
    var resources = [];

    if (window.performance.getEntriesByType !== undefined) {
      resources = window.performance.getEntriesByType("resource");
    } else if (window.performance.webkitGetEntriesByType !== undefined) {
      resources = window.performance.webkitGetEntriesByType("resource");
    }

    for (var n = 0; n < resources.length; n++) {
      entries.push(createEntryFromResourceTiming(resources[n]));
    }
    return entries;
  }

  /**
   * Creates an entry from a PerformanceResourceTiming object
   */
  function createEntryFromResourceTiming(resource) {
    return {
      url: resource.name,
      start: resource.startTime,
      duration: resource.duration,
      redirectStart: resource.redirectStart,
      redirectDuration: resource.redirectEnd - resource.redirectStart,
      appCacheStart: 0, // TODO
      appCacheDuration: 0, // TODO
      dnsStart: resource.domainLookupStart,
      dnsDuration: resource.domainLookupEnd - resource.domainLookupStart,
      tcpStart: resource.connectStart,
      tcpDuration: (resource.secureConnectionStart > 0 ? resource.secureConnectionStart : resource.connectEnd) - resource.connectStart,
      sslStart: resource.secureConnectionStart > 0 ? resource.secureConnectionStart : 0,
      sslDuration: resource.secureConnectionStart > 0 ? resource.connectEnd - resource.secureConnectionStart : 0,
      requestStart: resource.requestStart,
      requestDuration: resource.responseStart - resource.requestStart,
      responseStart: resource.responseStart,
      responseDuration: resource.responseStart == 0 ? 0 : resource.responseEnd - resource.responseStart
    };
  }

	// push.dataLayer
})();