91 lines
3.1 KiB
JavaScript
91 lines
3.1 KiB
JavaScript
Object.defineProperty(exports, '__esModule', { value: true });
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const types = require('../types.js');
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const bindReporter = require('./lib/bindReporter.js');
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const getActivationStart = require('./lib/getActivationStart.js');
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const getVisibilityWatcher = require('./lib/getVisibilityWatcher.js');
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const initMetric = require('./lib/initMetric.js');
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const observe = require('./lib/observe.js');
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const onHidden = require('./lib/onHidden.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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const reportedMetricIDs = {};
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/**
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* Calculates the [LCP](https://web.dev/lcp/) value for the current page and
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* calls the `callback` function once the value is ready (along with the
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* relevant `largest-contentful-paint` 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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const onLCP = (onReport) => {
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const visibilityWatcher = getVisibilityWatcher.getVisibilityWatcher();
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const metric = initMetric.initMetric('LCP');
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let report;
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const handleEntries = (entries) => {
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const lastEntry = entries[entries.length - 1] ;
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if (lastEntry) {
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// The startTime attribute returns the value of the renderTime if it is
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// not 0, and the value of the loadTime otherwise. The activationStart
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// reference is used because LCP should be relative to page activation
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// rather than navigation start if the page was prerendered.
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const value = Math.max(lastEntry.startTime - getActivationStart.getActivationStart(), 0);
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// Only report if the page wasn't hidden prior to LCP.
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if (value < visibilityWatcher.firstHiddenTime) {
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metric.value = value;
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metric.entries = [lastEntry];
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report();
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}
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}
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};
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const po = observe.observe('largest-contentful-paint', handleEntries);
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if (po) {
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report = bindReporter.bindReporter(onReport, metric);
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const stopListening = () => {
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if (!reportedMetricIDs[metric.id]) {
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handleEntries(po.takeRecords() );
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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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if (types.WINDOW.document) {
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addEventListener(type, stopListening, { once: true, capture: true });
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}
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});
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onHidden.onHidden(stopListening, true);
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return stopListening;
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}
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return;
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};
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exports.onLCP = onLCP;
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//# sourceMappingURL=getLCP.js.map
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