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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.
*/
import {onBFCacheRestore} from './lib/bfcache.js';
import {bindReporter} from './lib/bindReporter.js';
import {getVisibilityWatcher} from './lib/getVisibilityWatcher.js';
import {initMetric} from './lib/initMetric.js';
import {observe} from './lib/observe.js';
import {onHidden} from './lib/onHidden.js';
import {
firstInputPolyfill,
resetFirstInputPolyfill,
} from './lib/polyfills/firstInputPolyfill.js';
import {runOnce} from './lib/runOnce.js';
import {whenActivated} from './lib/whenActivated.js';
import {
FIDMetric,
FirstInputPolyfillCallback,
MetricRatingThresholds,
ReportOpts,
} from './types.js';
/** Thresholds for FID. See https://web.dev/articles/fid#what_is_a_good_fid_score */
export const FIDThresholds: MetricRatingThresholds = [100, 300];
/**
* Calculates the [FID](https://web.dev/articles/fid) value for the current page and
* calls the `callback` function once the value is ready, along with the
* relevant `first-input` performance entry used to determine the value. The
* reported value is a `DOMHighResTimeStamp`.
*
* _**Important:** since FID is only reported after the user interacts with the
* page, it's possible that it will not be reported for some page loads._
*/
export const onFID = (
onReport: (metric: FIDMetric) => void,
opts?: ReportOpts,
) => {
// Set defaults
opts = opts || {};
whenActivated(() => {
const visibilityWatcher = getVisibilityWatcher();
let metric = initMetric('FID');
let report: ReturnType<typeof bindReporter>;
const handleEntry = (entry: PerformanceEventTiming) => {
// Only report if the page wasn't hidden prior to the first input.
if (entry.startTime < visibilityWatcher.firstHiddenTime) {
metric.value = entry.processingStart - entry.startTime;
metric.entries.push(entry);
report(true);
}
};
const handleEntries = (entries: FIDMetric['entries']) => {
entries.forEach(handleEntry);
};
const po = observe('first-input', handleEntries);
report = bindReporter(
onReport,
metric,
FIDThresholds,
opts!.reportAllChanges,
);
if (po) {
onHidden(
runOnce(() => {
handleEntries(po.takeRecords() as FIDMetric['entries']);
po.disconnect();
}),
);
onBFCacheRestore(() => {
metric = initMetric('FID');
report = bindReporter(
onReport,
metric,
FIDThresholds,
opts!.reportAllChanges,
);
// Browsers don't re-emit FID on bfcache restore so fake it until you make it
resetFirstInputPolyfill();
firstInputPolyfill(handleEntry as FirstInputPolyfillCallback);
});
}
});
};
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