ecmascript 6 - ReactJS giving error Uncaught TypeError: Super expression must either be null or a function, not undefined

Question

I am using ReactJS.

When I run the code below the browser says:

Uncaught TypeError: Super expression must either be null or a function, not undefined

Any hints at all as to what is wrong would be appreciated.

First the line used to compile the code:

browserify -t reactify -t babelify examples/temp.jsx  -o examples/public/app.js

And the code:

var React = require('react');

class HelloMessage extends React.Component {
  render() {
    return <div>Hello </div>;
  }
}

UPDATE: After burning in hellfire for three days on this problem I found that I was not using the latest version of react.

Install globally:

sudo npm install -g [email protected]

install locally:

npm install [email protected]

make sure the browser is using the right version too:

<script type="text/javascript" src="react-0.13.2.js"></script>

Hope this saves someone else three days of precious life.

Answer 1

Class Names

Firstly, if you're certain that you're extending from the correctly named class, e.g. React.Component, not React.component or React.createComponent, you may need to upgrade your React version. See answers below for more information on the classes to extend from.

Upgrade React

React has only supported ES6-style classes since version 0.13.0 (see their official blog post on the support introduction here.

Before that, when using:

class HelloMessage extends React.Component

you were attempting to use ES6 keywords (extends) to subclass from a class which wasn't defined using ES6 class. This was likely why you were running into strange behaviour with super definitions etc.

So, yes, TL;DR - update to React v0.13.x.

Circular Dependencies

This can also occur if you have circular import structure. One module importing another and the other way around. In this case you just need to refactor your code to avoid it. More info