64 lines
2.6 KiB
JavaScript
64 lines
2.6 KiB
JavaScript
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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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import { bindReporter } from './lib/bindReporter.js';
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import { getVisibilityWatcher } from './lib/getVisibilityWatcher.js';
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import { initMetric } from './lib/initMetric.js';
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import { observe } from './lib/observe.js';
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import { onBFCacheRestore } from './lib/onBFCacheRestore.js';
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export const getFCP = (onReport, reportAllChanges) => {
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const visibilityWatcher = getVisibilityWatcher();
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let metric = initMetric('FCP');
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let report;
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const entryHandler = (entry) => {
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if (entry.name === 'first-contentful-paint') {
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if (po) {
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po.disconnect();
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}
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// Only report if the page wasn't hidden prior to the first paint.
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if (entry.startTime < visibilityWatcher.firstHiddenTime) {
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metric.value = entry.startTime;
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metric.entries.push(entry);
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report(true);
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}
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}
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};
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// TODO(philipwalton): remove the use of `fcpEntry` once this bug is fixed.
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// https://bugs.webkit.org/show_bug.cgi?id=225305
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// The check for `getEntriesByName` is needed to support Opera:
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// https://github.com/GoogleChrome/web-vitals/issues/159
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// The check for `window.performance` is needed to support Opera mini:
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// https://github.com/GoogleChrome/web-vitals/issues/185
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const fcpEntry = window.performance && performance.getEntriesByName &&
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performance.getEntriesByName('first-contentful-paint')[0];
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const po = fcpEntry ? null : observe('paint', entryHandler);
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if (fcpEntry || po) {
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report = bindReporter(onReport, metric, reportAllChanges);
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if (fcpEntry) {
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entryHandler(fcpEntry);
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}
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onBFCacheRestore((event) => {
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metric = initMetric('FCP');
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report = bindReporter(onReport, metric, reportAllChanges);
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requestAnimationFrame(() => {
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requestAnimationFrame(() => {
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metric.value = performance.now() - event.timeStamp;
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report(true);
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});
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});
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});
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}
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};
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