-
Notifications
You must be signed in to change notification settings - Fork 427
/
Copy pathonTTFB.ts
104 lines (94 loc) · 3.59 KB
/
onTTFB.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
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
/*
* 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 {initMetric} from './lib/initMetric.js';
import {onBFCacheRestore} from './lib/bfcache.js';
import {getNavigationEntry} from './lib/getNavigationEntry.js';
import {MetricRatingThresholds, ReportOpts, TTFBMetric} from './types.js';
import {getActivationStart} from './lib/getActivationStart.js';
import {whenActivated} from './lib/whenActivated.js';
/** Thresholds for TTFB. See https://web.dev/articles/ttfb#what_is_a_good_ttfb_score */
export const TTFBThresholds: MetricRatingThresholds = [800, 1800];
/**
* Runs in the next task after the page is done loading and/or prerendering.
* @param callback
*/
const whenReady = (callback: () => void) => {
if (document.prerendering) {
whenActivated(() => whenReady(callback));
} else if (document.readyState !== 'complete') {
addEventListener('load', () => whenReady(callback), true);
} else {
// Queue a task so the callback runs after `loadEventEnd`.
setTimeout(callback, 0);
}
};
/**
* Calculates the [TTFB](https://web.dev/articles/ttfb) value for the
* current page and calls the `callback` function once the page has loaded,
* along with the relevant `navigation` performance entry used to determine the
* value. The reported value is a `DOMHighResTimeStamp`.
*
* Note, this function waits until after the page is loaded to call `callback`
* in order to ensure all properties of the `navigation` entry are populated.
* This is useful if you want to report on other metrics exposed by the
* [Navigation Timing API](https://w3c.github.io/navigation-timing/). For
* example, the TTFB metric starts from the page's [time
* origin](https://www.w3.org/TR/hr-time-2/#sec-time-origin), which means it
* includes time spent on DNS lookup, connection negotiation, network latency,
* and server processing time.
*/
export const onTTFB = (
onReport: (metric: TTFBMetric) => void,
opts?: ReportOpts,
) => {
// Set defaults
opts = opts || {};
let metric = initMetric('TTFB');
let report = bindReporter(
onReport,
metric,
TTFBThresholds,
opts.reportAllChanges,
);
whenReady(() => {
const navigationEntry = getNavigationEntry();
if (navigationEntry) {
// The activationStart reference is used because TTFB should be
// relative to page activation rather than navigation start if the
// page was prerendered. But in cases where `activationStart` occurs
// after the first byte is received, this time should be clamped at 0.
metric.value = Math.max(
navigationEntry.responseStart - getActivationStart(),
0,
);
metric.entries = [navigationEntry];
report(true);
// Only report TTFB after bfcache restores if a `navigation` entry
// was reported for the initial load.
onBFCacheRestore(() => {
metric = initMetric('TTFB', 0);
report = bindReporter(
onReport,
metric,
TTFBThresholds,
opts!.reportAllChanges,
);
report(true);
});
}
});
};