callbacks-in-react-7.js

class MyParentComponent extends Component {
  constructor() {
    super()
    this.state = {
          somethingBoundToParent: 'How are you?'
    }
    this.onCallback = this.onCallback.bind(this)
  }

  onCallback(fromChildArg) {
    const { somethingBoundToParent } = this.state
    console.log(fromChildArg, somethingBoundToParent)
  }

  render() {
    <MyChildComponent callback={ this.onCallback } />
  }
}