39 lines
1.4 KiB
JavaScript
39 lines
1.4 KiB
JavaScript
/*
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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 { bindReporter } from './lib/bindReporter.js';
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import { getFirstHidden } from './lib/getFirstHidden.js';
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import { initMetric } from './lib/initMetric.js';
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import { observe } from './lib/observe.js';
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export const getFCP = (onReport) => {
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const metric = initMetric('FCP');
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const firstHidden = getFirstHidden();
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let report;
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const entryHandler = (entry) => {
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if (entry.name === 'first-contentful-paint') {
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// Only report if the page wasn't hidden prior to the first paint.
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if (entry.startTime < firstHidden.timeStamp) {
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metric.value = entry.startTime;
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metric.isFinal = true;
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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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};
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const po = observe('paint', entryHandler);
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if (po) {
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report = bindReporter(onReport, metric, po);
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}
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};
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