ES6 Reduce nested objects in an array

Question

I've been using map and reduce over some objects and arrays which have been working well so far, however I'm having trouble with one array.

Example of data here:

var arr =
[
[
{
  "id": 6501511,
  "invoiceId": {
    "id": 1043773
  },
  "chargeBandType": "TIME",
  "jobTaskId": {
    "id": 19399852
  },
  "invoicedNet": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "invoicedTaxOneOtherCurrency": null,
  "invoicedTaxOne": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "taxOneRate": 0.1
},
{
  "id": 6501517,
  "invoiceId": {
    "id": 1043773
  },
  "chargeBandType": "TIME",
  "jobTaskId": null,
  "jobExpenseId": null,
  "jobThirdPartyCostId": {
    "id": 20602
  },
  "invoicedNet": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "invoicedTaxOneOtherCurrency": null,
  "invoicedTaxOne": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "taxOneRate": 0.1
},
{
  "id": 6501508,
  "invoiceId": {
    "id": 13773
  },
  "chargeBandType": "TIME",
  "jobTaskId": {
    "id": 19398574
  },
  "invoicedNet": {
    "amountString": 30,
    "currencyType": "USD"
  },
  "invoicedTaxOneOtherCurrency": null,
  "invoicedTaxOne": {
    "amountString": 3,
    "currencyType": "USD"
  },
  "taxOneRate": 0.1
},
{
  "id": 65014,
  "invoiceId": {
    "id": 104
  },
  "chargeBandType": "TIME",
  "jobTaskId": null,
  "jobExpenseId": null,
  "jobThirdPartyCostId": {
    "id": 206
  },
  "invoicedNet": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "invoicedTaxOneOtherCurrency": null,
  "invoicedTaxOne": {
    "amountString": 0,
    "currencyType": "USD"
  },
  "taxOneRate": 0.1
}],
[
{
  "id": 6483,
  "invoiceId": {
    "id": 1042400
  },
  "chargeBandType": "TIME",
  "jobTaskId": {
    "id": 198574
  },
  "invoicedNet": {
    "amountString": 100,
    "currencyType": "USD"
  },
  "invoicedTaxOneOtherCurrency": null,
  "invoicedTaxOne": {
    "amountString": 10,
    "currencyType": "USD"
  },
  "taxOneRate": 0.1
}
]
];

I am trying to reduce the values of invoicedNet.amountString, which would bring a sum of 130 in the case above.

I have tried many ways to work this, including functions similar to the below:

var sum = arr.reduce(function(a, b) {
return a += b.invoicedNet.amountString;
}, 0);

However, no matter how I try this, I keep getting the error:

TypeError: Cannot read property 'amountString' of undefined

(It seems to pick up b.invoicedNet as an object though).

Could anyone suggest an approach to this?

Thanks!

Answer 1

You need to loop both arrays.

var arr = [[{ id: 6501511, invoiceId: { id: 1043773 }, chargeBandType: "TIME", jobTaskId: { id: 19399852 }, invoicedNet: { amountString: 0, currencyType: "USD" }, invoicedTaxOneOtherCurrency: null, invoicedTaxOne: { amountString: 0, currencyType: "USD" }, taxOneRate: 0.1 }, { id: 6501517, invoiceId: { id: 1043773 }, chargeBandType: "TIME", jobTaskId: null, jobExpenseId: null, jobThirdPartyCostId: { id: 20602 }, invoicedNet: { amountString: 0, currencyType: "USD" }, invoicedTaxOneOtherCurrency: null, invoicedTaxOne: { amountString: 0, currencyType: "USD" }, taxOneRate: 0.1 }, { id: 6501508, invoiceId: { id: 13773 }, chargeBandType: "TIME", jobTaskId: { id: 19398574 }, invoicedNet: { amountString: 30, currencyType: "USD" }, invoicedTaxOneOtherCurrency: null, invoicedTaxOne: { amountString: 3, currencyType: "USD" }, taxOneRate: 0.1 }, { id: 65014, invoiceId: { id: 104 }, chargeBandType: "TIME", jobTaskId: null, jobExpenseId: null, jobThirdPartyCostId: { id: 206 }, invoicedNet: { amountString: 0, currencyType: "USD" }, invoicedTaxOneOtherCurrency: null, invoicedTaxOne: { amountString: 0, currencyType: "USD" }, taxOneRate: 0.1 }], [{ id: 6483, invoiceId: { id: 1042400 }, chargeBandType: "TIME", jobTaskId: { id: 198574 }, invoicedNet: { amountString: 100, currencyType: "USD" }, invoicedTaxOneOtherCurrency: null, invoicedTaxOne: { amountString: 10, currencyType: "USD" }, taxOneRate: 0.1 }]],
    sum = arr.reduce(function (a, b) {
        b.forEach(function (c) {
            a += c.invoicedNet.amountString;
        });
        return a;
    }, 0);

console.log(sum);

Answer 2

You can do this quite neatly by flattening the arrays first and then reducing:

[].concat(...arr)
  .map(invoice => invoice.invoicedNet.amountString)
  .reduce((a, b) => a + b)