Add web-vitals measuring and event tracking (#2619)

Co-authored-by: Andrew Schamp <schamp@dropbox.com>

Author: schamp

Diff for: package.json

@@ -77,7 +77,8 @@
     "styled-components": "^5.0.1",
     "tar": "^6.0.1",
     "topojson-client": "^3.1.0",
-    "uuid": "^8.3.0"
+    "uuid": "^8.3.0",
+    "web-vitals": "^1.1.0"
   },
   "scripts": {
     "start": "cross-env TSC_COMPILE_ON_ERROR=false react-scripts -r @cypress/instrument-cra start",

Diff for: src/components/Analytics/index.ts

@@ -7,6 +7,7 @@ import {
   trackCopyLink,
   trackShare,
   trackVoteClick,
+  trackWebVitals,
 } from './utils';
 
 export default PageviewTracker;
@@ -19,4 +20,5 @@ export {
   trackCopyLink,
   trackShare,
   trackVoteClick,
+  trackWebVitals,
 };

Diff for: src/components/Analytics/utils.ts

@@ -44,6 +44,7 @@ export enum EventCategory {
   EXPOSURE_NOTIFICATIONS = 'exposure notifications',
   SEARCH = 'search',
   VACCINATION = 'vaccination',
+  WEB_VITALS = 'web vitals',
   NONE = 'none', // use NONE for development
 }
 
@@ -65,6 +66,11 @@ export enum EventAction {
   REDIRECT = 'redirect',
   FOCUS = 'focus',
   NAVIGATE = 'navigate',
+  CLS = 'Cumulative Layout Shift (*1000)',
+  FCP = 'First Contentful Paint (ms)',
+  FID = 'First Input Delay (ms)',
+  LCP = 'Largest Contentful Paint (ms)',
+  TTFB = 'Time to First Byte',
 }
 
 /**
@@ -77,9 +83,17 @@ export function trackEvent(
   label?: string,
   value?: number,
   nonInteraction?: boolean,
+  transport: 'beacon' | 'xhr' | 'image' = 'beacon',
 ) {
   if (category !== EventCategory.NONE) {
-    ReactGA.event({ category, action, label, value, nonInteraction });
+    ReactGA.event({
+      category,
+      action,
+      label,
+      value,
+      nonInteraction,
+      transport,
+    });
   }
 }
 
@@ -106,3 +120,34 @@ export function trackShare(label: string) {
 export function trackVoteClick(label: string) {
   trackEvent(EventCategory.VOTE_2020, EventAction.CLICK_LINK, label);
 }
+
+/**
+ * Callback passed to web-vitals to report important performance events
+ */
+export function trackWebVitals({
+  name,
+  delta,
+  id,
+}: {
+  name: 'CLS' | 'FID' | 'LCP' | 'FCP' | 'TTFB';
+  delta: number;
+  id: string;
+}) {
+  trackEvent(
+    EventCategory.WEB_VITALS,
+    EventAction[name],
+    // The `id` value will be unique to the current page load. When sending
+    // multiple values from the same page (e.g. for CLS), Google Analytics can
+    // compute a total by grouping on this ID (note: requires `eventLabel` to
+    // be a dimension in your report).
+    id,
+    // Google Analytics metrics must be integers, so the value is rounded.
+    // For CLS the value is first multiplied by 1000 for greater precision
+    // (note: increase the multiplier for greater precision if needed).
+    Math.round(name === 'CLS' ? delta * 1000 : delta),
+    // Use a non-interaction event to avoid affecting bounce rate.
+    true,
+    // Use `sendBeacon()` if the browser supports it.
+    'beacon',
+  );
+}

Diff for: src/index.js

@@ -3,6 +3,8 @@ import ReactDOM from 'react-dom';
 import './index.css';
 import App from './App';
 import * as serviceWorker from './serviceWorker';
+import reportWebVitals from './reportWebVitals';
+import { trackWebVitals } from './components/Analytics';
 import * as Sentry from '@sentry/react';
 import { initFullStory } from 'common/fullstory';
 
@@ -30,3 +32,5 @@ ReactDOM.render(<App />, document.getElementById('root'));
 // unregister() to register() below. Note this comes with some pitfalls.
 // Learn more about service workers: https://bit.ly/CRA-PWA
 serviceWorker.unregister();
+
+reportWebVitals(trackWebVitals);

Diff for: src/reportWebVitals.ts

@@ -0,0 +1,19 @@
+// implementation comes from a later version of create-react-app that this app was created from,
+// but the implementation seems worth reusing.
+// copied from https://github.com/facebook/create-react-app/blob/4e97dc75ad0c859fde7e2ffdaf9d5bd7d107b21a/packages/cra-template-typescript/template/src/reportWebVitals.ts
+
+import { ReportHandler } from 'web-vitals';
+
+const reportWebVitals = (onPerfEntry?: ReportHandler) => {
+  if (onPerfEntry && onPerfEntry instanceof Function) {
+    import('web-vitals').then(({ getCLS, getFID, getFCP, getLCP, getTTFB }) => {
+      getCLS(onPerfEntry);
+      getFID(onPerfEntry);
+      getFCP(onPerfEntry);
+      getLCP(onPerfEntry);
+      getTTFB(onPerfEntry);
+    });
+  }
+};
+
+export default reportWebVitals;

Diff for: yarn.lock

@@ -20417,6 +20417,11 @@ web-namespaces@^1.0.0:
   resolved "https://registry.yarnpkg.com/web-namespaces/-/web-namespaces-1.1.4.tgz#bc98a3de60dadd7faefc403d1076d529f5e030ec"
   integrity sha512-wYxSGajtmoP4WxfejAPIr4l0fVh+jeMXZb08wNc0tMg6xsfZXj3cECqIK0G7ZAqUq0PP8WlMDtaOGVBTAWztNw==
 
+web-vitals@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/web-vitals/-/web-vitals-1.1.0.tgz#7f410d9a1f7a1cd5d952806b45776204b47dc274"
+  integrity sha512-1cx54eRxY/+M0KNKdNpNnuXAXG+vJEvwScV4DiV9rOYDguHoeDIzm09ghBohOPtkqPO5OtPC14FWkNva3SDisg==
+
 webidl-conversions@^4.0.2:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/webidl-conversions/-/webidl-conversions-4.0.2.tgz#a855980b1f0b6b359ba1d5d9fb39ae941faa63ad"