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const result = data.reduce((acc, curr) => {
    // [curr.category.name]

    if (!curr.price) return acc;

    if (acc[curr.category]) {
        acc[curr.category] += Number(curr.price);
    } else {
        acc[curr.category] = Number(curr.price);
    }

    return acc;
},{});

const gastos = Object.entries(result);

const flatted = gastos.flatMap(el => {
    return {[el[0]]: el[1]};
});

console.log(flatted);