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/*
* 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.
*/
interface PerformanceEntryMap {
'event': PerformanceEventTiming[];
'first-input': PerformanceEventTiming[];
'layout-shift': LayoutShift[];
'largest-contentful-paint': LargestContentfulPaint[];
'long-animation-frame': PerformanceLongAnimationFrameTiming[];
'paint': PerformancePaintTiming[];
'navigation': PerformanceNavigationTiming[];
'resource': PerformanceResourceTiming[];
}
/**
* Takes a performance entry type and a callback function, and creates a
* `PerformanceObserver` instance that will observe the specified entry type
* with buffering enabled and call the callback _for each entry_.
*
* This function also feature-detects entry support and wraps the logic in a
* try/catch to avoid errors in unsupporting browsers.
*/
export const observe = <K extends keyof PerformanceEntryMap>(
type: K,
callback: (entries: PerformanceEntryMap[K]) => void,
opts?: PerformanceObserverInit,
): PerformanceObserver | undefined => {
try {
if (PerformanceObserver.supportedEntryTypes.includes(type)) {
const po = new PerformanceObserver((list) => {
// Delay by a microtask to workaround a bug in Safari where the
// callback is invoked immediately, rather than in a separate task.
// See: https://github.com/GoogleChrome/web-vitals/issues/277
Promise.resolve().then(() => {
callback(list.getEntries() as PerformanceEntryMap[K]);
});
});
po.observe(
Object.assign(
{
type,
buffered: true,
},
opts || {},
) as PerformanceObserverInit,
);
return po;
}
} catch (e) {
// Do nothing.
}
return;
};
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