web-vitals
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Easily measure performance metrics in JavaScript
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JavaScript
/*
* Copyright 2022 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.
*/
import { getLoadState } from '../lib/getLoadState.js';
import { getSelector } from '../lib/getSelector.js';
import { onINP as unattributedOnINP } from '../onINP.js';
const attributeINP = (metric) => {
if (metric.entries.length) {
const longestEntry = metric.entries.sort((a, b) => {
// Sort by: 1) duration (DESC), then 2) processing time (DESC)
return b.duration - a.duration || (b.processingEnd - b.processingStart) -
(a.processingEnd - a.processingStart);
})[0];
metric.attribution = {
eventTarget: getSelector(longestEntry.target),
eventType: longestEntry.name,
eventTime: longestEntry.startTime,
eventEntry: longestEntry,
loadState: getLoadState(longestEntry.startTime),
};
}
else {
metric.attribution = {};
}
};
/**
* Calculates the [INP](https://web.dev/responsiveness/) value for the current
* page and calls the `callback` function once the value is ready, along with
* the `event` performance entries reported for that interaction. The reported
* value is a `DOMHighResTimeStamp`.
*
* A custom `durationThreshold` configuration option can optionally be passed to
* control what `event-timing` entries are considered for INP reporting. The
* default threshold is `40`, which means INP scores of less than 40 are
* reported as 0. Note that this will not affect your 75th percentile INP value
* unless that value is also less than 40 (well below the recommended
* [good](https://web.dev/inp/#what-is-a-good-inp-score) threshold).
*
* If the `reportAllChanges` configuration option is set to `true`, the
* `callback` function will be called as soon as the value is initially
* determined as well as any time the value changes throughout the page
* lifespan.
*
* _**Important:** INP should be continually monitored for changes throughout
* the entire lifespan of a page—including if the user returns to the page after
* it's been hidden/backgrounded. However, since browsers often [will not fire
* additional callbacks once the user has backgrounded a
* page](https://developer.chrome.com/blog/page-lifecycle-api/#advice-hidden),
* `callback` is always called when the page's visibility state changes to
* hidden. As a result, the `callback` function might be called multiple times
* during the same page load._
*/
export const onINP = (onReport, opts) => {
unattributedOnINP(((metric) => {
attributeINP(metric);
onReport(metric);
}), opts);
};