subscribe redux store without react-redux

component.js

export class Component extends React.Component{

  mapState(state){
    return state;
  }

  shouldComponentUpdate(nextProps, nextState){
    if(Object.keys(nextState).length !== Object.keys(this.state).length ||
       Object.keys(nextProps).length !== Object.keys(this.props).length){
      return true;
    }
    for(let k in nextState){
      if(typeof nextState[k] === "object" ||
         this.state[k] !== nextState[k]) return true;
    }
    for(let k in nextProps){
      if(typeof nextProps[k] === "object" ||
         this.props[k] !== nextProps[k]) return true;
    }
    return false;
  }

  componentWillUnmount(){
    this.unsubscribeStore();
  }

  componentDidMount(){
    this.unsubscribeStore = store.subscribe(() => {
      this.setState(this.mapState(store.getState()));
    });
  }

  constructor(){
    super();
    this.state = this.mapState(store.getState());
  }

}