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56 lines
2.1 KiB
56 lines
2.1 KiB
2 months ago
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/*
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* Copyright 2022 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 { getBFCacheRestoreTime } from '../lib/bfcache.js';
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import { getLoadState } from '../lib/getLoadState.js';
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import { getNavigationEntry } from '../lib/getNavigationEntry.js';
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import { onFCP as unattributedOnFCP } from '../onFCP.js';
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const attributeFCP = (metric) => {
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if (metric.entries.length) {
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const navigationEntry = getNavigationEntry();
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const fcpEntry = metric.entries[metric.entries.length - 1];
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if (navigationEntry) {
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const activationStart = navigationEntry.activationStart || 0;
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const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
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metric.attribution = {
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timeToFirstByte: ttfb,
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firstByteToFCP: metric.value - ttfb,
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loadState: getLoadState(metric.entries[0].startTime),
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navigationEntry,
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fcpEntry,
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};
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return;
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}
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}
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// Set an empty object if no other attribution has been set.
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metric.attribution = {
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timeToFirstByte: 0,
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firstByteToFCP: metric.value,
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loadState: getLoadState(getBFCacheRestoreTime()),
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};
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};
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/**
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* Calculates the [FCP](https://web.dev/fcp/) value for the current page and
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* calls the `callback` function once the value is ready, along with the
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* relevant `paint` performance entry used to determine the value. The reported
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* value is a `DOMHighResTimeStamp`.
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*/
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export const onFCP = (onReport, opts) => {
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unattributedOnFCP(((metric) => {
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attributeFCP(metric);
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onReport(metric);
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}), opts);
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};
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