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interactionCountPolyfill.ts
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interactionCountPolyfill.ts
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/*
* 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 {observe} from '../observe.js';
import {Metric, PerformanceEventTiming} from '../../types.js';
declare global {
interface Performance {
interactionCount: number;
}
}
let interactionCountEstimate = 0;
let minKnownInteractionId = Infinity;
let maxKnownInteractionId = 0;
const updateEstimate = (entries: Metric['entries']) => {
(entries as PerformanceEventTiming[]).forEach((e) => {
if (e.interactionId) {
minKnownInteractionId = Math.min(minKnownInteractionId, e.interactionId);
maxKnownInteractionId = Math.max(maxKnownInteractionId, e.interactionId);
interactionCountEstimate = maxKnownInteractionId ?
(maxKnownInteractionId - minKnownInteractionId) / 7 + 1 : 0;
}
});
}
let po: PerformanceObserver | undefined;
/**
* Returns the `interactionCount` value using the native API (if available)
* or the polyfill estimate in this module.
*/
export const getInteractionCount = () => {
return po ? interactionCountEstimate : performance.interactionCount || 0;
}
/**
* Feature detects native support or initializes the polyfill if needed.
*/
export const initInteractionCountPolyfill = () => {
if ('interactionCount' in performance || po) return;
po = observe(['event'], updateEstimate, {
type: 'event',
buffered: true,
durationThreshold: 0,
} as PerformanceObserverInit);
};