import { WINDOW } from '../types.js'; import { bindReporter } from './lib/bindReporter.js'; import { getActivationStart } from './lib/getActivationStart.js'; import { getVisibilityWatcher } from './lib/getVisibilityWatcher.js'; import { initMetric } from './lib/initMetric.js'; import { observe } from './lib/observe.js'; import { onHidden } from './lib/onHidden.js'; /* * Copyright 2020 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. */ const reportedMetricIDs = {}; /** * Calculates the [LCP](https://web.dev/lcp/) value for the current page and * calls the `callback` function once the value is ready (along with the * relevant `largest-contentful-paint` performance entry used to determine the * value). The reported value is a `DOMHighResTimeStamp`. */ const onLCP = (onReport) => { const visibilityWatcher = getVisibilityWatcher(); const metric = initMetric('LCP'); let report; const handleEntries = (entries) => { const lastEntry = entries[entries.length - 1] ; if (lastEntry) { // The startTime attribute returns the value of the renderTime if it is // not 0, and the value of the loadTime otherwise. The activationStart // reference is used because LCP should be relative to page activation // rather than navigation start if the page was prerendered. const value = Math.max(lastEntry.startTime - getActivationStart(), 0); // Only report if the page wasn't hidden prior to LCP. if (value < visibilityWatcher.firstHiddenTime) { metric.value = value; metric.entries = [lastEntry]; report(); } } }; const po = observe('largest-contentful-paint', handleEntries); if (po) { report = bindReporter(onReport, metric); const stopListening = () => { if (!reportedMetricIDs[metric.id]) { handleEntries(po.takeRecords() ); po.disconnect(); reportedMetricIDs[metric.id] = true; report(true); } }; // Stop listening after input. Note: while scrolling is an input that // stop LCP observation, it's unreliable since it can be programmatically // generated. See: https://github.com/GoogleChrome/web-vitals/issues/75 ['keydown', 'click'].forEach(type => { if (WINDOW.document) { addEventListener(type, stopListening, { once: true, capture: true }); } }); onHidden(stopListening, true); return stopListening; } return; }; export { onLCP }; //# sourceMappingURL=getLCP.js.map