React selector use case

mapStateToProps-vs-Selector.js

// Store Redux
state = {
 cars: {
   carsById: {
     1: { id: 1, name "Toyota" },
     2: { id: 2, name "Lexus" },
     3: { id: 3, name "Honda" }
   }
 }
};

// selectors.js
const carsSelector = state => state.cars.carsById;
export const getCarsSelector = createSelector(carsSelector, carsById => Object.values(carsById));

// CarListPage.js
class CarListPage extends PureComponent {
  ...
  render() {
    return (
      <div className="myClass">
        {this.props.cars.map(car => <CarComponent car={car} />)}
      </div>
    );
  };
  ...
}
  
const mapStateToProps = state => {
  return {
    cars: getCarsSelector(state)
  };
};