Get the total value of the matching array elements

Question

This is my current array

0:{modelNumber: "123456789", balance: { amount:1000, currency:"EUR" }}
1:{modelNumber: "987654321", balance: { amount:2000, currency:"EUR" }}
2:{modelNumber: "322353466", balance: { amount:1500, currency:"GBP" }}
3:{modelNumber: "892347522", balance: { amount:1000, currency:"USD" }}
4:{modelNumber: "931883113", balance: { amount:3000, currency:"INR" }}
5:{modelNumber: "854300564", balance: { amount:2500, currency:"GBP" }}
6:{modelNumber: "931883113", balance: { amount:3000, currency:"INR" }}
7:{modelNumber: "854300564", balance: { amount:3500, currency:"USD" }}

I'm trying to return a new array, with each currency and the total value for each currency.

Like below return the total amount for each currency in the array above

0:{currency: "EUR", totalAmount: 3500}
1:{currency: "GBP", totalAmount: 5000}
2:{currency: "USD", totalAmount: 4500}
3:{currency: "INR", totalAmount: 6000}

My approach initially:

//the current array
let theInitialArray = state.vehicle;

const results = theInitialArray.reduce((accumalator, current) => {
    const { currency } = current.balance;
    if (accumalator[currency]) {
        accumalator[currency].push(current);
        return accumalator;
    }
    accumalator[currency] = [current];
    return accumalator;     
}, {});

let frank =  Object.keys(results)
let jim = [];
let expectedOutput = theInitialArray.filter((x) => {
    for (let i=0; i < frank.length; i++) {
        if (x.balance.currency === frank[i]) {
            jim.push({'currency': frank[i], 'amount': x.balance.amount});
        }
    }
});
console.log('expectedOutput', expectedOutput)
return expectedOutput

Answer 1

You can Array.reduce() to iterate the data. If a currency doesn't exist in the accumulator (r in the reduce callback), initialize it. Add the current amount, to the currency amount in the accumulator. Get an array of currencies using Object.values:

const data = [{"modelNumber":"123456789","balance":{"amount":1000,"currency":"EUR"}},{"modelNumber":"987654321","balance":{"amount":2000,"currency":"EUR"}},{"modelNumber":"322353466","balance":{"amount":1500,"currency":"GBP"}},{"modelNumber":"892347522","balance":{"amount":1000,"currency":"USD"}},{"modelNumber":"931883113","balance":{"amount":3000,"currency":"INR"}},{"modelNumber":"854300564","balance":{"amount":2500,"currency":"GBP"}},{"modelNumber":"931883113","balance":{"amount":3000,"currency":"INR"}},{"modelNumber":"854300564","balance":{"amount":3500,"currency":"USD"}}];

const result = Object.values(data.reduce((r, { balance }) => {
  const { amount, currency } = balance;
  if(!r[currency]) r[currency] = { currency, amount: 0 };
  
  r[currency].amount += amount;
  
  return r;
}, {}));

console.log(result);

Answer 2

A simple solution with Array.prototype.reduce and Object.keys:

const data = [
    {modelNumber: "123456789", balance: { amount:1000, currency:"EUR" }},
    {modelNumber: "987654321", balance: { amount:2000, currency:"EUR" }},
    {modelNumber: "322353466", balance: { amount:1500, currency:"GBP" }},
    {modelNumber: "892347522", balance: { amount:1000, currency:"USD" }},
    {modelNumber: "931883113", balance: { amount:3000, currency:"INR" }},
    {modelNumber: "854300564", balance: { amount:2500, currency:"GBP" }},
    {modelNumber: "931883113", balance: { amount:3000, currency:"INR" }},
    {modelNumber: "854300564", balance: { amount:3500, currency:"USD" }}
];

const grouped = data.reduce((o, { balance: { amount:a, currency:c } }) =>
   ({...o, [c]: (o[c] || 0) + a }), {});

const result = Object.keys(grouped).map(currency =>
    ({currency, totalAmount: grouped[currency] }));

console.log(result);