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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.
*/
export const getNavigationEntry = (): PerformanceNavigationTiming | void => {
const navigationEntry =
self.performance &&
performance.getEntriesByType &&
performance.getEntriesByType('navigation')[0];
// Check to ensure the `responseStart` property is present and valid.
// In some cases no value is reported by the browser (for
// privacy/security reasons), and in other cases (bugs) the value is
// negative or is larger than the current page time. Ignore these cases:
// https://github.com/GoogleChrome/web-vitals/issues/137
// https://github.com/GoogleChrome/web-vitals/issues/162
// https://github.com/GoogleChrome/web-vitals/issues/275
if (
navigationEntry &&
navigationEntry.responseStart > 0 &&
navigationEntry.responseStart < performance.now()
) {
return navigationEntry;
}
};
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