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