Count identical objects by 2 properties in an array and introduce a count property

Question

Trying to count a few objects in an array of objects so that it checks 2 properties and if they are the same, it increases the count.

Edit: basically, I want to check the itemId and the orderId and if there is another object with the same values in the array, I want to increase the count

input =>
[{itemName: "Burger", itemId: 111, orderId: 123},
 {itemName: "Burger", itemId: 111, orderId: 123},
 {itemName: "Pizza",  itemId: 222, orderId: 456}]

output =>
[{itemName: "Burger", itemId: 111, orderId: 123, count: 2},
 {itemName: "Pizza",  itemId: 222, orderId: 456, count: 1}]

I tried to use a reduce function and a simple forEach but the closest I got was:

counter = {}
myArray.forEach(function(obj) {
    var key = JSON.stringify(obj)
    counter[key] = (counter[key] || 0) + 1
})

result => 
[{itemName: "Burger", itemId: 111, orderId: 123}: 2,
 {itemName: "Pizza",  itemId: 222, orderId: 456}: 1 ]

Can I get some help with this please?

Jamiec · Accepted Answer · 2021-02-12 12:18:58Z

1

You can use a combination of Object.values and Array.prototype.reduce:

var input = [{itemName: "Burger", itemId: 111, orderId: 123},
 {itemName: "Burger", itemId: 111, orderId: 123},
 {itemName: "Pizza",  itemId: 222, orderId: 456}];
 
 var result = Object.values(input.reduce( (acc, i) => {
  var key = JSON.stringify(i)
  return {
    ...acc,
    [key]: {...i, count: (acc[key]?.count || 0) + 1}
  }
 },{}));
 
 console.log(result)

edited Feb 12, 2021 at 12:18

answered Feb 12, 2021 at 12:08

Jamiec

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