Uncaught ReferenceError: ReactDOM is not defined

Question

So i have Rails applications, i installed react-rails gem, set it up and try to run test application.

Freshly installed, when i tryed to run hello world program, this er

Answer 1

It may be the spelling issue - it is ReactDOM, not ReactDom.

This has changed over time with the new release of React

Answer 2

To make it work properly, you have to do 3 things.

1. Import the CDNs, necessary for the developement(Say react and react-dom for web development)

<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>

2. install babel-cli . It is needed for the compilation of JSX into vanila js

3. change the typo in your code,

it is ReactDOM , not RaactDOM

Answer 3

You have to import it

import ReactDOM from 'react-dom';

Answer 4

Make sure that you've included react-dom.js. You can add it from CDN or use js toolchain of your choice.

Installing React - using a CDN

<script src="https://unpkg.com/react@15/dist/react.js"></script>
<script src="https://unpkg.com/react-dom@15/dist/react-dom.js"></script>

Answer 5

ReactDOM available since version 0.14.0, so you need to use React.render (because you have a React version 0.13.3) instead,

setInterval(function() {
  React.render(
    <HelloWorld date={new Date()} />,
    document.getElementById('example')
  );
}, 500);

or upgrade your React version and include ReactDOM

Changes in React 0.14