77 lines
3.6 KiB
JavaScript
77 lines
3.6 KiB
JavaScript
/*
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* Copyright 2022 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { onTTFB as unattributedOnTTFB } from '../onTTFB.js';
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const attributeTTFB = (metric) => {
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// Use a default object if no other attribution has been set.
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let attribution = {
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waitingDuration: 0,
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cacheDuration: 0,
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dnsDuration: 0,
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connectionDuration: 0,
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requestDuration: 0,
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};
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if (metric.entries.length) {
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const navigationEntry = metric.entries[0];
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const activationStart = navigationEntry.activationStart || 0;
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// Measure from workerStart or fetchStart so any service worker startup
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// time is included in cacheDuration (which also includes other sw time
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// anyway, that cannot be accurately split out cross-browser).
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const waitEnd = Math.max((navigationEntry.workerStart || navigationEntry.fetchStart) -
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activationStart, 0);
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const dnsStart = Math.max(navigationEntry.domainLookupStart - activationStart, 0);
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const connectStart = Math.max(navigationEntry.connectStart - activationStart, 0);
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const connectEnd = Math.max(navigationEntry.connectEnd - activationStart, 0);
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attribution = {
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waitingDuration: waitEnd,
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cacheDuration: dnsStart - waitEnd,
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// dnsEnd usually equals connectStart but use connectStart over dnsEnd
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// for dnsDuration in case there ever is a gap.
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dnsDuration: connectStart - dnsStart,
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connectionDuration: connectEnd - connectStart,
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// There is often a gap between connectEnd and requestStart. Attribute
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// that to requestDuration so connectionDuration remains 0 for
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// service worker controlled requests were connectStart and connectEnd
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// are the same.
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requestDuration: metric.value - connectEnd,
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navigationEntry: navigationEntry,
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};
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}
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// Use Object.assign to set property to keep tsc happy.
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const metricWithAttribution = Object.assign(metric, { attribution });
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return metricWithAttribution;
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};
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/**
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* Calculates the [TTFB](https://web.dev/articles/ttfb) value for the
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* current page and calls the `callback` function once the page has loaded,
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* along with the relevant `navigation` performance entry used to determine the
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* value. The reported value is a `DOMHighResTimeStamp`.
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*
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* Note, this function waits until after the page is loaded to call `callback`
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* in order to ensure all properties of the `navigation` entry are populated.
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* This is useful if you want to report on other metrics exposed by the
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* [Navigation Timing API](https://w3c.github.io/navigation-timing/). For
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* example, the TTFB metric starts from the page's [time
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* origin](https://www.w3.org/TR/hr-time-2/#sec-time-origin), which means it
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* includes time spent on DNS lookup, connection negotiation, network latency,
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* and server processing time.
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*/
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export const onTTFB = (onReport, opts) => {
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unattributedOnTTFB((metric) => {
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const metricWithAttribution = attributeTTFB(metric);
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onReport(metricWithAttribution);
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}, opts);
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};
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