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70 lines
2.9 KiB
70 lines
2.9 KiB
2 years ago
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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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import { onHidden } from './lib/onHidden.js';
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const reportedMetricIDs = {};
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export const getLCP = (onReport, reportAllChanges) => {
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const visibilityWatcher = getVisibilityWatcher();
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let metric = initMetric('LCP');
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let report;
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const entryHandler = (entry) => {
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// The startTime attribute returns the value of the renderTime if it is not 0,
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// and the value of the loadTime otherwise.
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const value = entry.startTime;
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// If the page was hidden prior to paint time of the entry,
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// ignore it and mark the metric as final, otherwise add the entry.
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if (value < visibilityWatcher.firstHiddenTime) {
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metric.value = value;
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metric.entries.push(entry);
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report();
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}
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};
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const po = observe('largest-contentful-paint', entryHandler);
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if (po) {
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report = bindReporter(onReport, metric, reportAllChanges);
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const stopListening = () => {
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if (!reportedMetricIDs[metric.id]) {
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po.takeRecords().map(entryHandler);
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po.disconnect();
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reportedMetricIDs[metric.id] = true;
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report(true);
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}
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};
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// Stop listening after input. Note: while scrolling is an input that
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// stop LCP observation, it's unreliable since it can be programmatically
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// generated. See: https://github.com/GoogleChrome/web-vitals/issues/75
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['keydown', 'click'].forEach((type) => {
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addEventListener(type, stopListening, { once: true, capture: true });
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});
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onHidden(stopListening, true);
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onBFCacheRestore((event) => {
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metric = initMetric('LCP');
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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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reportedMetricIDs[metric.id] = true;
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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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