Array of objects to another array sumarized

Question

I'm new to JS and I'm having issues to sum values from one array into another one summarized.

I have this data:

const data = [
  {
    category: 'personal',
    amount: 80000,
    month: 'Diciembre',
  },
  {
    category: 'comida',
    amount: 207000,
    month: 'Diciembre',
  },
  {
    category: 'comida',
    amount: 43000,
    month: 'Diciembre',
  },
  {
    category: 'salidas',
    amount: 124000,
    month: 'Diciembre',
  },
  {
    category: 'casa',
    amount: 450505,
    month: 'Diciembre',
  },
  {
    category: 'casa',
    amount: 500000,
    month: 'Diciembre',
  },
  {
    category: 'varios',
    amount: 260000,
    month: 'Diciembre',
  },
  {
    category: 'casa',
    amount: 296300,
    month: 'Diciembre',
  },
];

And I want to convert it in something like:

const dataSummarized = [
  {
    category: 'personal',
    amount: TOTAL_AMOUNT_PERSONAL_CATEGORY
    month: 'Diciembre',
  },
  {
    category: 'comida',
    amount: TOTAL_AMOUNT_COMIDA_CATEGORY
    month: 'Diciembre',
  },
  {
    category: 'salidas',
    amount: TOTAL_AMOUNT_SALIDAS_CATEGORY,
    month: 'Diciembre',
  },
  {
    category: 'casa',
    amount: TOTAL_AMOUNT_CASA_CATEGORY,
    month: 'Diciembre',
  }
];

I've tried several options, but without results.

Some of the solutions I've tried are posted here Sum javascript object propertyA values with same object propertyB in array of objects

Evidently, I'm missing something because I couldn't make it work :(

Thanks in advance!

Please share what you've tried based on the answers from Sum javascript object propertyA values with same object propertyB in array of objects and what didn't work, otherwise, people will most likely point you back in the direction of the answers from there. — Nick Parsons
– Nick Parsons, Commented Dec 7, 2021 at 11:21
"I've tried several options" - consider adding these efforts to the question as minimal reproducible examples? — evolutionxbox
– evolutionxbox, Commented Dec 7, 2021 at 11:22

Terry Lennox · Accepted Answer · 2021-12-07 11:27:42Z

We can then use Array.reduce() to group items by category, then month (I presume you want expense totals per month).

We create a grouping key based on category and month, then sum the total amount for each of these keys:

const data = [ { category: 'personal', amount: 80000, month: 'Diciembre', }, { category: 'comida', amount: 207000, month: 'Diciembre', }, { category: 'comida', amount: 43000, month: 'Diciembre', }, { category: 'salidas', amount: 124000, month: 'Diciembre', }, { category: 'casa', amount: 450505, month: 'Diciembre', }, { category: 'casa', amount: 500000, month: 'Diciembre', }, { category: 'varios', amount: 260000, month: 'Diciembre', }, { category: 'casa', amount: 296300, month: 'Diciembre', }, ]; 

const result = Object.values(data.reduce((acc, { category, month, amount }) => { 
    const key = `${category}-${month}`;
    acc[key] = acc[key] || { category, month, amount: 0 };
    acc[key].amount += amount;
    return acc;
}, {}));

console.log('Result:', result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

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