57 lines
1.7 KiB
TypeScript
57 lines
1.7 KiB
TypeScript
/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import {initMetric} from './lib/initMetric.js';
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import {observe, PerformanceEntryHandler} from './lib/observe.js';
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import {onHidden} from './lib/onHidden.js';
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import {bindReporter} from './lib/bindReporter.js';
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import {ReportHandler} from './types.js';
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// https://wicg.github.io/layout-instability/#sec-layout-shift
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interface LayoutShift extends PerformanceEntry {
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value: number;
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hadRecentInput: boolean;
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}
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export const getCLS = (onReport: ReportHandler, reportAllChanges = false) => {
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const metric = initMetric('CLS', 0);
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let report: ReturnType<typeof bindReporter>;
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const entryHandler = (entry: LayoutShift) => {
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// Only count layout shifts without recent user input.
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if (!entry.hadRecentInput) {
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(metric.value as number) += entry.value;
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metric.entries.push(entry);
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report();
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}
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};
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const po = observe('layout-shift', entryHandler as PerformanceEntryHandler);
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if (po) {
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report = bindReporter(onReport, metric, po, reportAllChanges);
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onHidden(({isUnloading}) => {
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po.takeRecords().map(entryHandler as PerformanceEntryHandler);
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if (isUnloading) {
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metric.isFinal = true;
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}
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report();
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});
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}
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};
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