71 lines
3.0 KiB
JavaScript
71 lines
3.0 KiB
JavaScript
/*
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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 { onBFCacheRestore } from './lib/bfcache.js';
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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 { onHidden } from './lib/onHidden.js';
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import { firstInputPolyfill, resetFirstInputPolyfill, } from './lib/polyfills/firstInputPolyfill.js';
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import { runOnce } from './lib/runOnce.js';
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import { whenActivated } from './lib/whenActivated.js';
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/** Thresholds for FID. See https://web.dev/articles/fid#what_is_a_good_fid_score */
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export const FIDThresholds = [100, 300];
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/**
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* Calculates the [FID](https://web.dev/articles/fid) 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 `first-input` performance entry used to determine the value. The
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* reported value is a `DOMHighResTimeStamp`.
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*
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* _**Important:** since FID is only reported after the user interacts with the
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* page, it's possible that it will not be reported for some page loads._
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*/
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export const onFID = (onReport, opts) => {
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// Set defaults
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opts = opts || {};
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whenActivated(() => {
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const visibilityWatcher = getVisibilityWatcher();
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let metric = initMetric('FID');
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let report;
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const handleEntry = (entry) => {
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// Only report if the page wasn't hidden prior to the first input.
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if (entry.startTime < visibilityWatcher.firstHiddenTime) {
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metric.value = entry.processingStart - 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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const handleEntries = (entries) => {
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entries.forEach(handleEntry);
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};
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const po = observe('first-input', handleEntries);
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report = bindReporter(onReport, metric, FIDThresholds, opts.reportAllChanges);
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if (po) {
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onHidden(runOnce(() => {
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handleEntries(po.takeRecords());
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po.disconnect();
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}));
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onBFCacheRestore(() => {
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metric = initMetric('FID');
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report = bindReporter(onReport, metric, FIDThresholds, opts.reportAllChanges);
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// Browsers don't re-emit FID on bfcache restore so fake it until you make it
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resetFirstInputPolyfill();
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firstInputPolyfill(handleEntry);
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});
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}
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});
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};
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