src/containers/book-list.js
//Purpose of this function is to take our application state and whatever gets returned will show up as props inside of BookList.

Purpose of this function is to take our application state and whatever gets returned will show up as props inside of BookList.
Purpose of this function is to take our application state and whatever gets returned will show up as props inside of BookList .
function mapStateToProps(state) {
    return {
        books: state.books          
    };                              
}                                   
function mapStateToProps ( state ) { return { books : state . books } ; }
Purpose of this function is to take our application state and whatever gets returned will show up as props inside of BookList.
Purpose of this function is to take our application state and whatever gets returned will show up as props inside of BookList .
//We want to have access to this.props.books within our component.  
 //So we return an object with a key of books and a value of state.books.
 //If our state ever changes this container will instantly re-render with a new list of books. 
