1 | /*
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2 | * Copyright 2020 Google LLC
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3 | *
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4 | * Licensed under the Apache License, Version 2.0 (the "License");
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5 | * you may not use this file except in compliance with the License.
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6 | * You may obtain a copy of the License at
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7 | *
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8 | * https://www.apache.org/licenses/LICENSE-2.0
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9 | *
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10 | * Unless required by applicable law or agreed to in writing, software
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11 | * distributed under the License is distributed on an "AS IS" BASIS,
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 | * See the License for the specific language governing permissions and
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14 | * limitations under the License.
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15 | */
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16 | import { onBFCacheRestore } from './lib/bfcache.js';
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17 | import { bindReporter } from './lib/bindReporter.js';
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18 | import { getVisibilityWatcher } from './lib/getVisibilityWatcher.js';
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19 | import { initMetric } from './lib/initMetric.js';
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20 | import { observe } from './lib/observe.js';
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21 | import { onHidden } from './lib/onHidden.js';
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22 | import { firstInputPolyfill, resetFirstInputPolyfill, } from './lib/polyfills/firstInputPolyfill.js';
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23 | import { runOnce } from './lib/runOnce.js';
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24 | import { whenActivated } from './lib/whenActivated.js';
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25 | /** Thresholds for FID. See https://web.dev/articles/fid#what_is_a_good_fid_score */
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26 | export const FIDThresholds = [100, 300];
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27 | /**
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28 | * Calculates the [FID](https://web.dev/articles/fid) value for the current page and
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29 | * calls the `callback` function once the value is ready, along with the
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30 | * relevant `first-input` performance entry used to determine the value. The
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31 | * reported value is a `DOMHighResTimeStamp`.
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32 | *
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33 | * _**Important:** since FID is only reported after the user interacts with the
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34 | * page, it's possible that it will not be reported for some page loads._
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35 | */
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36 | export const onFID = (onReport, opts) => {
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37 | // Set defaults
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38 | opts = opts || {};
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39 | whenActivated(() => {
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40 | const visibilityWatcher = getVisibilityWatcher();
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41 | let metric = initMetric('FID');
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42 | let report;
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43 | const handleEntry = (entry) => {
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44 | // Only report if the page wasn't hidden prior to the first input.
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45 | if (entry.startTime < visibilityWatcher.firstHiddenTime) {
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46 | metric.value = entry.processingStart - entry.startTime;
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47 | metric.entries.push(entry);
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48 | report(true);
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49 | }
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50 | };
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51 | const handleEntries = (entries) => {
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52 | entries.forEach(handleEntry);
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53 | };
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54 | const po = observe('first-input', handleEntries);
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55 | report = bindReporter(onReport, metric, FIDThresholds, opts.reportAllChanges);
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56 | if (po) {
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57 | onHidden(runOnce(() => {
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58 | handleEntries(po.takeRecords());
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59 | po.disconnect();
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60 | }));
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61 | onBFCacheRestore(() => {
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62 | metric = initMetric('FID');
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63 | report = bindReporter(onReport, metric, FIDThresholds, opts.reportAllChanges);
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64 | // Browsers don't re-emit FID on bfcache restore so fake it until you make it
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65 | resetFirstInputPolyfill();
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66 | firstInputPolyfill(handleEntry);
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67 | });
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68 | }
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69 | });
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70 | };
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