Uncaught ReferenceError: React is not defined

Question

Hi I know this type of question has been asked quite a few times but I couldn't get the answer.

I am trying to write a React hello world example. I have only two files one app.jsx and another homepage.jsx. I am using webpack to bundle the files.

But when I run the code I get Uncaught ReferenceError: React is not defined

My homepage.jsx looks like this

"use strict";  var React = require('react');  var Home = React.createClass({     render : function() {         return (             <div className="jumbotron">                                 <h1> Hello World</h1>              </div>         );     } });  module.exports = Home; 

My app.js looks like this

var ReactDOM = require('react-dom');  var Home = require('./components/homePage');  ReactDOM.render(   <Home/>,   document.getElementById('app') ); 

In browser it throws Uncaught ReferenceError: React is not defined at line 7 i.e where I am requiring homepage.

But when I add var React = require('react') in app.jsx it works fine.

I don't understand this. I have included react in homepage.jsx where I am making use of it. In app.jsx I only require react-dom becuase I don't use React. Then why it is giving error in app.jsx.

Pls help!!

Answer 1

Change your app.js to this

var React = require('react'); var ReactDOM = require('react-dom');  var Home = require('./components/homePage');  ReactDOM.render(     <Home/>,     document.getElementById('app') ); 

JSX is transformed into React.createElement() calls, thus React is required in scope. So yes, you are using React in app.js. Get used to import it whenever you use JSX or direct React.* calls.

Answer 2

You can have it without require it in your code.

Add to webpack.config.js:

plugins: [   new webpack.ProvidePlugin({     "React": "react",   }), ], 

See https://webpack.js.org/plugins/provide-plugin/#root