How to breakdown an array of objects?

I have an array of objects and i need to classify each object by name and then get the addition of some properties.

To be more specific, I have a cart with some orders and i need to breakdown by product name so i can calculate how many items of that product were bought.

const orders = [
{
    name: 'Isaac',
    products: [
      {
        name: 'Apple',
        unit: 'x6 und',
        qty: 1
      },
      {
        name: 'Lemon',
        unit: '500gr',
        qty: 2
      },
      {
        name: 'Coconut',
        unit: 'x3 und',
        qty: 1
      },
      {
        name: 'Orange',
        unit: 'kg',
        qty: 1
      },
    ]
  },
  {
    name: 'Andrea',
    products: [
      {
        name: 'Apple',
        unit: 'x6 und',
        qty: 2
      },
      {
        name: 'Lemon',
        unit: '500gr',
        qty: 3
      },
      {
        name: 'Coconut',
        unit: 'x3 und',
        qty: 2
      },
      {
        name: 'Garlic',
        unit: '250 gr',
        qty: 2
      },
    ]
  },
  {
    name: 'George',
    products: [
      {
        name: 'Apple',
        unit: 'x6 und',
        qty: 3
      },
      {
        name: 'Lemon',
        unit: '500gr',
        qty: 4
      },
      {
        name: 'Coconut',
        unit: 'x3 und',
        qty: 3
      },
      {
        name: 'Garlic',
        unit: '250 gr',
        qty: 1
      },
    ]
  }
]

That is the dummy data,

I mapped the orders array and then mapped the products array, then i used .flat() method to get another array of objects but simplified.

Now I am stuck.

const resume = orders.map(order => {
return order.products.map(prods => {
    return prods
  })
})

console.log(resume.flat());

This is the result:

    [
  { name: 'Apple', unit: 'x6 und', qty: 1 },
  { name: 'Lemon', unit: '500gr', qty: 2 },
  { name: 'Coconut', unit: 'x3 und', qty: 1 },
  { name: 'Orange', unit: 'kg', qty: 1 },
  { name: 'Apple', unit: 'x12 und', qty: 2 },
  { name: 'Apple', unit: 'x6 und', qty: 2 },
  { name: 'Lemon', unit: '500gr', qty: 3 },
  { name: 'Coconut', unit: 'x3 und', qty: 2 },
  { name: 'Garlic', unit: '250 gr', qty: 2 },
  { name: 'Apple', unit: 'x6 und', qty: 3 },
  { name: 'Lemon', unit: '500gr', qty: 4 },
  { name: 'Coconut', unit: 'x3 und', qty: 3 },
  { name: 'Garlic', unit: '250 gr', qty: 1 }
]

At this point, i need to know how many apples, Coconut, Garlic were sold.

Example: name: ‘Apple’, unit: ‘X6 und’, qty: 6 name: ‘Apple’, unit: ‘X12 und’, qty: 1 name: ‘Lemon’, unit: ‘500gr’, qty: 9 an so on…

Any clue? I am completely lost 🙁

Answer

Probably not as elegant as reduce, but kind of fun, is the following: Starting with your original orders (no need for the intermediate step, unless you want it), initiate an empty array, like ordersArray = [], and run the following:

orders.forEach((order) => {
  order.products.forEach((product) => {
    const index = ordersArray.findIndex((prod) => prod.name === product.name);
      index === -1 ? ordersArray.push(product) : ordersArray[index].qty += product.qty  
  });
});

Your result is:

ordersArray = [
   { name: 'Apple', unit: 'x6 und', qty: 6 },
   { name: 'Lemon', unit: '500gr', qty: 9 },
   { name: 'Coconut', unit: 'x3 und', qty: 6 },
   { name: 'Orange', unit: 'kg', qty: 1 },
   { name: 'Garlic', unit: '250 gr', qty: 3 },
 ]

This looks right (I’m not sure where the { name: 'Apple', unit: 'x12 und', qty: 2 } object came from for your intermediate step 🙂 ). Lately, I’ve been storing this kind of information in an object (see here). It would be very similar, with only slight differences: Start with the same orders (obviously), and then define an empty object ordersObject = {}.

orders.forEach((order) => {
  order.products.forEach((product) => {
    ordersObject[product.name] = { unit: product.unit, qty: (ordersObject[product.name]?.qty || 0) + product.qty }
  });
});

The result is similar, but easier to update, retrieve data, etc.

ordersObject = {
  Apple: { unit: 'x6 und', qty: 6 },
  Lemon: { unit: '500gr', qty: 9 },
  Coconut: { unit: 'x3 und', qty: 6 },
  Orange: { unit: 'kg', qty: 1 },
  Garlic: { unit: '250 gr', qty: 3 }
}