sample-reactjs-component-es6.js

class Sample extends Component{
  state = { value: 0 };
  
  _onClick(){
    this.setState({
      value: value + 1
    });
  }
  
  render(){
    return(
      <div>
        <span>{ this.state.value }</span>
        <span onClick={ this._onClick.bind(this) }>+</span>
      </div>
    );
  }
}