getFID.ts
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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 {bindReporter} from './lib/bindReporter.js';
import {getFirstHidden} from './lib/getFirstHidden.js';
import {initMetric} from './lib/initMetric.js';
import {observe, PerformanceEntryHandler} from './lib/observe.js';
import {onHidden} from './lib/onHidden.js';
import {ReportHandler} from './types.js';
interface FIDPolyfillCallback {
(value: number, event: Event): void;
}
interface FIDPolyfill {
onFirstInputDelay: (onReport: FIDPolyfillCallback) => void;
}
declare global {
interface Window {
perfMetrics: FIDPolyfill;
}
}
// https://wicg.github.io/event-timing/#sec-performance-event-timing
interface PerformanceEventTiming extends PerformanceEntry {
processingStart: DOMHighResTimeStamp;
cancelable?: boolean;
target?: Element;
}
export const getFID = (onReport: ReportHandler) => {
const metric = initMetric('FID');
const firstHidden = getFirstHidden();
const entryHandler = (entry: PerformanceEventTiming) => {
// Only report if the page wasn't hidden prior to the first input.
if (entry.startTime < firstHidden.timeStamp) {
metric.value = entry.processingStart - entry.startTime;
metric.entries.push(entry);
metric.isFinal = true;
report();
}
};
const po = observe('first-input', entryHandler as PerformanceEntryHandler);
const report = bindReporter(onReport, metric, po);
if (po) {
onHidden(() => {
po.takeRecords().map(entryHandler as PerformanceEntryHandler);
po.disconnect();
}, true);
} else {
if (window.perfMetrics && window.perfMetrics.onFirstInputDelay) {
window.perfMetrics.onFirstInputDelay((value: number, event: Event) => {
// Only report if the page wasn't hidden prior to the first input.
if (event.timeStamp < firstHidden.timeStamp) {
metric.value = value;
metric.isFinal = true;
metric.entries = [{
entryType: 'first-input',
name: event.type,
target: event.target,
cancelable: event.cancelable,
startTime: event.timeStamp,
processingStart: event.timeStamp + value,
} as PerformanceEventTiming];
report();
}
});
}
}
};