looping over objects javascript

Question

So recently I learned about using for in loops to loop over objects. We were given this problem to solve regarding a basic cart object that contains name of object and then quantity and price.

const cart = {
  "Gold Round Sunglasses": { quantity: 1, priceInCents: 1000 },
  "Pink Bucket Hat": { quantity: 2, priceInCents: 1260 },
};

We have to write 2 functions, one that calculates total cost of inventory in cents and the other displays the inventory.

The calculateCartTotal function will take in the cart and return a total price, in cents, of everything inside of it.
The printCartInventory function will take in the cart and return a string, joined by \n, of the quantity and name of each item.

I was able to the finish question one with ease but am struggling with the 2nd one.

1st function:

function calculateCartTotal(cart) {
  let total = 0;
  for(let item in cart){
    const product = cart[item]
    const quantity = product.quantity
    const price = product.priceInCents
    total += quantity * price
  }
  return total
}

2nd function:

function printCartInventory(cart) {
  let inventory = ""
  for(let item in cart){
    const product = cart[item]
    const quantity = product.quantity
    inventory += `${quantity}x${product}/n`
  }
  return inventory
}

When I test the 2nd function the autograder gives this error:

expected '2x[object Object]/n1x[object Object]/n1x[object Object]/n3x[object Object]/n' to include '2xCanvas Tote Bag\n1xBlack and White Chuck On Dress\n1xNatural Straw Wide Brim Hat\n3xBlue Stripe Casual Shirt'

product is an object. The default toString of an object returns "[object Object]". Instead of using the default toString output you should print what you actually want from the object (e.g., specific properties, a meaningful representation of a property, etc). There are several ways to do that; the easiest would be something like ${product.quantity} and so on. — Dave Newton
– Dave Newton, Commented Sep 22, 2022 at 18:59
To me it looks like the names of your product are the keys of the object. This is a bit gross, but you can fix your code with const product = item; instead of cart[item] (or just use the item variable instead of product) — James
– James, Commented Sep 22, 2022 at 19:01
Recommend checking out map and reduce. The first function can be rewritten in one line: const cartTotal = cart.reduce((total, item) => total + (item.quantity * item.priceInCents), 0); — TrueWill
– TrueWill, Commented Sep 22, 2022 at 19:50

trincot · Accepted Answer · 2022-09-22 20:09:19Z

1

When you look at the error message, note the part that says [object Object]. This is part of your code's output, and should ring a bell. It means your code tries to put an object in a string, instead of a string.

The guilty code is here:

inventory += `${quantity}x${product}/n`

product is not a string, but an object. It is not what you intended to output there. What you want to output is the name of the product, which is the key, not the value associated with that key. So it should be:

inventory += `${quantity}x${item}/n`

edited Sep 22, 2022 at 20:09

answered Sep 22, 2022 at 19:39

trincot

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