Write object-oriented code to model a till.

The objects under test:

• The Product represents a product with an id, label, and price
• The Catalog lists all available products available at the shop
• The Till lists purchased products and generates bill

Simply run yarn install at the top-level to install the required modules.

Then run jest to run all tests.

All tests in the-oop-till.test.js should be made to pass. You can start with the first test at the top and make your way down. Do not modify the tests. You should be able to make them pass simply by fleshing out the code under test.

The code starts out using prototypal inheritance: you can just flesh out the function definitions and make judicious use of the this keyword.

Once your tests are passing, convert your objects to ES6 class syntax. For example, a skeleton of the Product class would look like this:

class Product {
  constructor(id, label, preTaxPrice){
  }

  getId(){
  }

  getPreTaxPrice(){
  }

  getLineItemDescription(){
  }
}

Some consider constructor functions and classes an anti-pattern in JavaScript.

• How would you model the till without resorting to classes?
• How could Object.create help you?
• The Till object needs the catalog to generate the bill. An alternative design would be to mix in the catalog functionality into the Till object. How would you do that?