Discussion on: Help? .map .reduce

[I am Budi]

This kind of question is better placed in stackoverflow.

var data = [
  { name: 'test1', category: 'Categoria1', price: 3 },
  { name: 'test2', category: 'Categoria1', price: 13.6 },
  { name: 'test3', category: 'Categoria2', price: 8 },
  { name: 'test4', category: 'Categoria2', price: 8 },
];

var result = {};
data.forEach(item => {
  const cat = item.category;
  if (result[cat] == undefined) {
    result[cat] = 0;
  }
  result[cat] += item.price;
});

console.log(Object.entries(result));
// output: [['Categoria1', 16.6],['Categoria2', 16]]
// simpler without map reduce

[cristiantsantos]

Thank you,

where do I find stackoverflow?

Thanks again, but the code didn't work

[I am Budi]

You can find here stackoverflow.com
For the code that didn't work above try here playcode

[ecyrbe]

For those reading this in the future :

Budi answer is much faster to execute than the one i provided above.

My approach is using functionnal js, no mutated data. For small data tables, it's ok.

But using Budi aproach is much faster if your dataset is large.

[Duy K. Bui]

we can do it purely functional too

const input = [
  {name: "test1", category: "Categoria1", price: 3},
  {name: "test2", category: "Categoria1", price: 13.6},
  {name: "test3", category: "Categoria2", price: 8},
  {name: "test4", category: "Categoria2", price: 8}
];
const map = input
  .map((item) => [item. category, item.price])
  .reduce((result, current) => {
    if (result[current[0]] === undefined) result[current[0]] = 0;
    result[current[0]] += result[current[1]];
    return result;
  }, {});
const output = Object.keys(result).map((key) => [key, result[key]])