Babel unexpected token compiling react component

Question

I'm trying to compile the following code using babel but it's giving me an "unexpected token" on the character "=" on the following line:

state = {};

Babel version is: 6.24.1 (babel-core 6.25.0)

The code:

import {Button, Menu} from 'semantic-ui-react';

class AppBar extends Component {
    state = {};

    handleItemClick = (e, { name }) => this.setState({ activeItem: name });

    render() {
        const { activeItem } = this.state;

        return (
            <Menu>
                <Menu.Item
                    name='dashboard'
                    active={activeItem === 'dashboard'}
                    onClick={this.handleItemClick}
                >
                    Dashboard
                </Menu.Item>

                <Menu.Item
                    name='contacts'
                    active={activeItem === 'contacts'}
                    onClick={this.handleItemClick}
                >
                    Contact Lists
                </Menu.Item>

                <Menu.Item
                    name='messages'
                    active={activeItem === 'messages'}
                    onClick={this.handleItemClick}
                >
                    Messages
                </Menu.Item>
            </Menu>
        )
    }
}

ReactDOM.render(
  <AppBar/>,
  document.getElementById('root')
);

I'm using the es2015 and react presets.

What is the problem? Thanks.

Answer 1

Add package babel-plugin-transform-class-properties to your project.

Answer 2

I'm currently using these babel modules (in the package.json) for our React app:

"babel-cli": "~6.24.1",
"babel-core": "~6.25.0",
"babel-eslint": "~7.2.3",
"babel-loader": "~7.1.0",
"babel-plugin-add-module-exports": "~0.2.1",
"babel-plugin-istanbul": "^4.1.3",
"babel-plugin-syntax-dynamic-import": "^6.18.0",
"babel-plugin-transform-class-properties": "~6.24.1",
"babel-preset-es2015": "~6.24.1",
"babel-preset-react": "~6.24.1",
"babel-preset-stage-3": "^6.24.1",
"babel-register": "~6.24.1",
"babel-runtime": "~6.23.0",

And I've the following .bablerc on the root folder:

{
  "presets": [
    "es2015", "react", "stage-3"
  ],
  "plugins": ["transform-class-properties", "add-module-exports","syntax-dynamic-import"],
  "env": {
    "development": {
      "plugins": ["react-hot-loader/babel"]
    },
    "coverage": {
      "plugins": ["istanbul"]
    }
  }
}

And I define state using the same code

export class AttributeModelListContainer extends React.Component {

  static propTypes = {
    // from router
    params: PropTypes.shape({
      project: PropTypes.string,
    }),
    // from mapStateToProps
    [...]
  }

  state = {
    isLoading: true,
  }
}