web-vitals/dist/modules/lib/whenIdleOrHidden.js

Easily measure performance metrics in JavaScript

/*
 * Copyright 2024 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 { runOnce } from './runOnce.js';
/**
 * Runs the passed callback during the next idle period, or immediately
 * if the browser's visibility state is (or becomes) hidden.
 */
export const whenIdleOrHidden = (cb) => {
    const rIC = globalThis.requestIdleCallback || setTimeout;
    // If the document is hidden, run the callback immediately, otherwise
    // race an idle callback with the next `visibilitychange` event.
    if (document.visibilityState === 'hidden') {
        cb();
    }
    else {
        cb = runOnce(cb);
        document.addEventListener('visibilitychange', cb, { once: true });
        rIC(() => {
            cb();
            // Remove the above event listener since no longer required.
            // See: https://github.com/GoogleChrome/web-vitals/issues/622
            document.removeEventListener('visibilitychange', cb);
        });
    }
};