112 lines
5.5 KiB
JavaScript
112 lines
5.5 KiB
JavaScript
/*
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* Copyright 2022 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 { initMetric } from './lib/initMetric.js';
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import { DEFAULT_DURATION_THRESHOLD, processInteractionEntry, estimateP98LongestInteraction, resetInteractions, } from './lib/interactions.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 { initInteractionCountPolyfill } from './lib/polyfills/interactionCountPolyfill.js';
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import { whenActivated } from './lib/whenActivated.js';
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import { whenIdle } from './lib/whenIdle.js';
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/** Thresholds for INP. See https://web.dev/articles/inp#what_is_a_good_inp_score */
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export const INPThresholds = [200, 500];
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/**
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* Calculates the [INP](https://web.dev/articles/inp) value for the current
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* page and calls the `callback` function once the value is ready, along with
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* the `event` performance entries reported for that interaction. The reported
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* value is a `DOMHighResTimeStamp`.
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*
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* A custom `durationThreshold` configuration option can optionally be passed to
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* control what `event-timing` entries are considered for INP reporting. The
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* default threshold is `40`, which means INP scores of less than 40 are
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* reported as 0. Note that this will not affect your 75th percentile INP value
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* unless that value is also less than 40 (well below the recommended
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* [good](https://web.dev/articles/inp#what_is_a_good_inp_score) threshold).
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*
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* If the `reportAllChanges` configuration option is set to `true`, the
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* `callback` function will be called as soon as the value is initially
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* determined as well as any time the value changes throughout the page
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* lifespan.
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*
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* _**Important:** INP should be continually monitored for changes throughout
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* the entire lifespan of a page—including if the user returns to the page after
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* it's been hidden/backgrounded. However, since browsers often [will not fire
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* additional callbacks once the user has backgrounded a
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* page](https://developer.chrome.com/blog/page-lifecycle-api/#advice-hidden),
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* `callback` is always called when the page's visibility state changes to
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* hidden. As a result, the `callback` function might be called multiple times
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* during the same page load._
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*/
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export const onINP = (onReport, opts) => {
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// Return if the browser doesn't support all APIs needed to measure INP.
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if (!('PerformanceEventTiming' in self &&
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'interactionId' in PerformanceEventTiming.prototype)) {
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return;
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}
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// Set defaults
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opts = opts || {};
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whenActivated(() => {
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// TODO(philipwalton): remove once the polyfill is no longer needed.
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initInteractionCountPolyfill();
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let metric = initMetric('INP');
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let report;
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const handleEntries = (entries) => {
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// Queue the `handleEntries()` callback in the next idle task.
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// This is needed to increase the chances that all event entries that
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// occurred between the user interaction and the next paint
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// have been dispatched. Note: there is currently an experiment
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// running in Chrome (EventTimingKeypressAndCompositionInteractionId)
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// 123+ that if rolled out fully may make this no longer necessary.
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whenIdle(() => {
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entries.forEach(processInteractionEntry);
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const inp = estimateP98LongestInteraction();
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if (inp && inp.latency !== metric.value) {
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metric.value = inp.latency;
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metric.entries = inp.entries;
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report();
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}
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});
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};
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const po = observe('event', handleEntries, {
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// Event Timing entries have their durations rounded to the nearest 8ms,
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// so a duration of 40ms would be any event that spans 2.5 or more frames
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// at 60Hz. This threshold is chosen to strike a balance between usefulness
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// and performance. Running this callback for any interaction that spans
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// just one or two frames is likely not worth the insight that could be
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// gained.
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durationThreshold: opts.durationThreshold ?? DEFAULT_DURATION_THRESHOLD,
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});
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report = bindReporter(onReport, metric, INPThresholds, opts.reportAllChanges);
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if (po) {
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// Also observe entries of type `first-input`. This is useful in cases
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// where the first interaction is less than the `durationThreshold`.
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po.observe({ type: 'first-input', buffered: true });
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onHidden(() => {
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handleEntries(po.takeRecords());
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report(true);
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});
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// Only report after a bfcache restore if the `PerformanceObserver`
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// successfully registered.
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onBFCacheRestore(() => {
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resetInteractions();
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metric = initMetric('INP');
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report = bindReporter(onReport, metric, INPThresholds, opts.reportAllChanges);
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});
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}
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});
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};
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