/
onFCP.ts
62 lines (56 loc) · 2.3 KB
/
onFCP.ts
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
/*
* Copyright 2022 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 {getBFCacheRestoreTime} from '../lib/bfcache.js';
import {getLoadState} from '../lib/getLoadState.js';
import {getNavigationEntry} from '../lib/getNavigationEntry.js';
import {onFCP as unattributedOnFCP} from '../onFCP.js';
import {FCPMetric, FCPMetricWithAttribution, FCPReportCallback, FCPReportCallbackWithAttribution, ReportOpts} from '../types.js';
const attributeFCP = (metric: FCPMetric): void => {
if (metric.entries.length) {
const navigationEntry = getNavigationEntry();
const fcpEntry = metric.entries[metric.entries.length - 1];
if (navigationEntry) {
const activationStart = navigationEntry.activationStart || 0;
const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
(metric as FCPMetricWithAttribution).attribution = {
timeToFirstByte: ttfb,
firstByteToFCP: metric.value - ttfb,
loadState: getLoadState(metric.entries[0].startTime),
navigationEntry,
fcpEntry,
};
return;
}
}
// Set an empty object if no other attribution has been set.
(metric as FCPMetricWithAttribution).attribution = {
timeToFirstByte: 0,
firstByteToFCP: metric.value,
loadState: getLoadState(getBFCacheRestoreTime()),
};
};
/**
* Calculates the [FCP](https://web.dev/fcp/) value for the current page and
* calls the `callback` function once the value is ready, along with the
* relevant `paint` performance entry used to determine the value. The reported
* value is a `DOMHighResTimeStamp`.
*/
export const onFCP = (onReport: FCPReportCallbackWithAttribution, opts?: ReportOpts) => {
unattributedOnFCP(((metric: FCPMetricWithAttribution) => {
attributeFCP(metric);
onReport(metric);
}) as FCPReportCallback, opts);
};