Sum up values of identical objects' property in Javascript array

Question

I have the following array:

[
 { name: "iPhone 12", quantity: 12, price: 325, … },
 { name: "iPhone 12", quantity: 4, price: 325, … },
 { name: "iPhone 13", quantity: 2, price: 525, … },
 { name: "iPhone 12", quantity: 2, price: 325 },
 { name: "iPhone 13", quantity: 3, price: 525 },
 { name: "iPhone SE", quantity: 2, price: 59 }
]

And I want to sum the quantity properties of each object in order to have an array with distinct elements like this:

[
  { name: "iPhone 12", quantity: 18, price: 325 },
  { name: "iPhone 13", quantity: 5, price: 525 },
  { name: "iPhone SE", quantity: 2, price: 59 }
]

How can I do that?

Answer 1

Seems like a good task for Array.prototype.reduce

 const data = [{ name: "iPhone 12", quantity: 12, price: 325, }, { name: "iPhone 12", quantity: 4, price: 325, }, { name: "iPhone 13", quantity: 2, price: 525, }, { name: "iPhone 12", quantity: 2, price: 325 }, { name: "iPhone 13", quantity: 3, price: 525 }, ] const summed = data.reduce((sum, current) => { const item = sum.find(el => el.name === current.name) if (item) { for (const key in item) { if (key === 'name') continue item[key] += current[key] } } else { sum.push({...current }) } return sum }, []) console.log(summed)