reduce-repeated-products.js

const nameKey = 'numero'
const quantityKey = 'qtd'

const product = [1, 1, 2, 2, 2, 3, 4, 5, 5]
const reduced = product.reduce((acc, num) => ({
  ...acc,
  [num.toString()]: ((acc && acc[num] || 0) + 1) 
}), {})

const formated = Object.keys(reduced).map((num) => ({
  [nameKey]: num,
  [quantityKey]: reduced[num]
}))

// ref: https://www.facebook.com/groups/877782458986503/permalink/3405796499518407