Sup #2

index.js

class App extends Component {
  // return false = COMPONENT_SHOULD_NOT_UPDATE!
  // return true = COMPONENT_SHOULD_UPDATE!
  shouldComponentUpdate(nextProps, nextState) {
    // PureComponent do this for you, not for everything tho
    return this.props.value != nextProps.value;
  }
  
  render() {
    return (
      <div>
        <h2>{this.props.value}</h2>
      </div>
    )
  }
}