ContextType

static contextType.jsx

import ShopContext from '../context/shop-context'

class CartPage extends Component {
  static contextType = ShopContext

  componentDidMount() {
    // Some advantage of static contextType: We can now also access Context in the rest of the component
    console.log(this.context)
  }

  render() {
    return (
      <React.Fragment>
        <Navigation
          cartItemNumber={this.context.cart.reduce((count, curItem) => {
            return count + curItem.quantity
          }, 0)}
        />
        <main className="cart">...</main>
      </React.Fragment>
    )
  }
}

export default CartPage