Initial state with ES6 classes, when defined in constructor

App.js

import React, { Component } from 'react';

class App2 extends Component {
    constructor( props ) {
        super( props );
        this.state = {
            message: 'world'
        }
    }
    render() {
        return (
            <h1>Hello {this.state.message} in ES6 classes</h1>
        );
    }
}

export default App2;