connectHOC_selector1.js

function connectHOC(mapStateToProps, mapDispatchToProps) {
  return function wrapWithConnect(WrappedComponent) {
    class Connect extends Component {
      constructor(props, context) {
        super(props, context)
        this.store = context.store
        this.initSelector()
        // ...subscribtion
      }
      initSelector() {
        //selector: (reduxStore.state + ownProps) => injected mergedProps 
        this.selector = simpleSelector //the one we defined in the medium story
      }
      //data source 1: store state change
      onStateChange() {
        this.selectorProps = this.selector(store.state, nextProps)
        this.setState({})
      }
      //data source 2: ownProps change
      componentWillReceiveProps(nextProps) {
        this.selectorProps = this.selector(store.state, nextProps)
      }
      componentDidUpdate() {
        //after the current component get updated, go ahead and notify the nested subscription
        this.subscription.notifyNestedSubs()
      }
      render() {
        return createElement(WrappedComponent, this.selectorProps) //get the mergedProps from the selector 
      }
    }
    return Connect;
  }
}