react-constructor-example.js

export default class ExampleComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      name: "John"
    };
    this.changeName = this.changeName.bind(this);
  }

  changeName() {
    this.setState({ name: "Bob" });
  }

  render() {
    return <h1 onClick={this.changeName}>{this.state.name}</h1>;
  }
}