93 lines
3.4 KiB
JavaScript
93 lines
3.4 KiB
JavaScript
import { WINDOW } from '../types.js';
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import { bindReporter } from './lib/bindReporter.js';
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import { getActivationStart } from './lib/getActivationStart.js';
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import { getNavigationEntry } from './lib/getNavigationEntry.js';
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import { initMetric } from './lib/initMetric.js';
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/*
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* Copyright 2020 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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/**
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* Runs in the next task after the page is done loading and/or prerendering.
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* @param callback
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*/
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const whenReady = (callback) => {
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if (!WINDOW.document) {
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return;
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}
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if (WINDOW.document.prerendering) {
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addEventListener('prerenderingchange', () => whenReady(callback), true);
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} else if (WINDOW.document.readyState !== 'complete') {
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addEventListener('load', () => whenReady(callback), true);
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} else {
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// Queue a task so the callback runs after `loadEventEnd`.
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setTimeout(callback, 0);
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}
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};
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/**
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* Calculates the [TTFB](https://web.dev/time-to-first-byte/) 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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const onTTFB = (onReport, opts) => {
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// Set defaults
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// eslint-disable-next-line no-param-reassign
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opts = opts || {};
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// https://web.dev/ttfb/#what-is-a-good-ttfb-score
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// const thresholds = [800, 1800];
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const metric = initMetric('TTFB');
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const report = bindReporter(onReport, metric, opts.reportAllChanges);
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whenReady(() => {
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const navEntry = getNavigationEntry() ;
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if (navEntry) {
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// The activationStart reference is used because TTFB should be
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// relative to page activation rather than navigation start if the
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// page was prerendered. But in cases where `activationStart` occurs
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// after the first byte is received, this time should be clamped at 0.
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metric.value = Math.max(navEntry.responseStart - getActivationStart(), 0);
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// In some cases the value reported is negative or is larger
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// than the current page time. Ignore these cases:
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// https://github.com/GoogleChrome/web-vitals/issues/137
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// https://github.com/GoogleChrome/web-vitals/issues/162
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if (metric.value < 0 || metric.value > performance.now()) return;
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metric.entries = [navEntry];
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report(true);
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}
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});
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};
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export { onTTFB };
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//# sourceMappingURL=onTTFB.js.map
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