rlrh/js-basics-online-shopping-lab-js-intro-000

Online Shopping

Objectives

• Model a shopping cart full of items as an array of objects in JavaScript.
• Practice dynamically setting properties (keys) of an object.
• Work with Object.keys() and .hasOwnProperty() to retrieve and verify an object's keys.
• Iterate over arrays with for loops
• Use ES6 ${template literals} instead of "regular, " + "old " + string + " concatenation."
• Brush up on conditionals and control flow to make some Oxford comma magic happen.

Instructions

We've started you off with a cart variable that points at an empty array. There are five functions that you'll have to code in order to create a working shopping cart:

1. The addToCart() function accepts one argument, the name of an item.
   • Use that passed-in string to create a new object representing the item. The object should consist of one key-value pair in which the key is the item's name and the value is a randomly-generated price: { itemName: itemPrice }. As more items are added, the cart should start to look something like this: [ { "bananas": 17 }, { "pancake batter": 5 }, { "eggs": 49 }].
   • The price of each item should be a randomly-generated integer between 1 and 100.
     • HINT: Look into Math.random() and Math.floor().
   • If you're struggling to create a new object from the item name, remember that ES6 provides a nifty way to dynamically set the keys in an object literal. That is, it allows the use of variables as keys. If you're having trouble recalling the syntax, take a look back at the Top Tip in the JavaScript Objects lesson.
   • Upon the successful addition of a new item to the cart, the function should print <itemName> has been added to your cart. to the console and then return the updated cart.
2. The viewCart() function does not accept any arguments. It should loop over every item in your cart, printing out the contents as one long, coherent statement in this format: In your cart, you have bananas at $17, pancake batter at $5, and eggs at $49.
   • If the cart is empty, the function should instead print out Your shopping cart is empty.
   • Note: Pay close attention to the syntax above. The printed statement should be a single sentence that begins with In your cart, you have , terminates in a period, and can assume the following shapes according to how many items the cart contains:
     • 1 item — In your cart, you have bananas at $17.
     • 2 items — In your cart, you have bananas at $17 and pancake batter at $5.
     • 3+ items — In your cart, you have bananas at $17, pancake batter at $5, and eggs at $49.
3. The total() function accepts no arguments, iterates through the cart array, and returns the current total value of the items in the cart.
4. The removeFromCart() function accepts one argument, the name of the item that should be removed.
   • If the cart does not contain a matching item, the function should print out That item is not in your cart. and return the unchanged cart.
   • If the item is present in the cart, the function should remove the object from the cart and then return the updated cart.
   • HINT: Check each object's key (the name of the item) to see if it matches the parameter, then remove it if it matches. You might find hasOwnProperty to be useful.
5. The placeOrder() function accepts one argument, a credit card number.
   • If no argument is received, the function should print out Sorry, we don't have a credit card on file for you..
   • If a card number is received, the function should print out Your total cost is $71, which will be charged to the card 83296759. (where 71 is the value returned by total() and 83296759 is the credit card number passed to placeOrder()). Then, it should empty the cart array.

The final send-off

This lab is not easy! The methods, especially viewCart() require careful planning and a sharp eye. The cart array is a non-trivial nested data structure, and it would be a good idea to periodically check the value of your variables (think: console.log(), debugger, etc.) at different points within your functions, especially when attempting to iterate over the cart and its items.

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