Wednesday, May 18, 2022

Uncaught TypeError: Cannot read properties of undefined (reading 'add') - React Helmet

 I was getting the below error while using the react-helmet to dynamically change the head section - meta tags, title etc, also the pages were not loading.

scheduler.development.js:171 Uncaught TypeError: Cannot read properties of undefined (reading 'add')

    at e.r.init (Dispatcher.js:53:1)

    at e.r.render (Dispatcher.js:67:1)

    at finishClassComponent (react-dom.development.js:17485:1)

    at updateClassComponent (react-dom.development.js:17435:1)

    at beginWork (react-dom.development.js:19073:1)

    at HTMLUnknownElement.callCallback (react-dom.development.js:3945:1)

    at Object.invokeGuardedCallbackDev (react-dom.development.js:3994:1)

    at invokeGuardedCallback (react-dom.development.js:4056:1)

    at beginWork$1 (react-dom.development.js:23964:1)

    at performUnitOfWork (react-dom.development.js:22776:1)

    at workLoopSync (react-dom.development.js:22707:1)

    at renderRootSync (react-dom.development.js:22670:1)

    at performSyncWorkOnRoot (react-dom.development.js:22293:1)

    at react-dom.development.js:11327:1

    at unstable_runWithPriority (scheduler.development.js:468:1)

    at runWithPriority$1 (react-dom.development.js:11276:1)

    at flushSyncCallbackQueueImpl (react-dom.development.js:11322:1)

    at workLoop (scheduler.development.js:417:1)

    at flushWork (scheduler.development.js:390:1)

    at MessagePort.performWorkUntilDeadline (scheduler.development.js:157:1)

To fix the issue

Replaced react-helmet with  react-helmet-async

npm install react-helmet-async or yarn add react-helmet-async

Wrap the App element with HelmetProvider

import { HelmetProvider } from 'react-helmet-async';




    <App />





Now the helmet can be used in individual components to change the dynamic header elements

import { Helmet } from 'react-helmet';

import {  Test   } from './components';

const Test = () => {

  return (




<meta name="description" content="Test Description" />

<meta property="og:title" content="Test"/>

<meta property="og:description" content="Test" />


  <Introduction />

  <Details />

  <BackToTop />




export default Test;

After this, I saw the behavior, non of the existing meta tags defined in index.html apart from the title, replaced with the new values. To fix that, I added data-rh="true" to the metatags in index.html that require the change.

<meta property="og:title" content="default value" data-rh="true" />

Somehow data-react-helmet=" true"  property was not working.

Happy Coding!!!

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