array of objects filter and sum by similar numbers

Question

I have this array of object and I need to get the sum of the amount column that has number greater than 3 and the same first 3 digits.

The object is :

Acc Number        Amount

1             -5425

10               12

100             100

    1000        -4971

    1001        84000

    1002          500

    1003         6411

101               654

    1010          245

102               288

    1020           21

    1021           68

    1020          -87

    1023          -668

The resulting object should be like below by suming all the 4 digits acc number after each similar 3 digits acc number e.g. sum of acc number 1000,1001,1002,1003(under acc number 100) gives 85,940

[

  {
    desc: "1",
    Amount: 5424
  }

  {
    desc: "10",
    Amount: 12
  }
  {
    desc: "100",
    Amount: 100
  }

 {
    desc: "1000 ",
    Amount: -4971
 }


 {
    desc: "1001 ",
    Amount: 84000
 }

 {
    desc: "1002 ",
    Amount: 500
 }

 {
    desc: "1005 ",
    Amount: 6411
 }

 {
   desc: "Sum account 100 with 4 digits",
   Amount: 85940
 }

 {
   desc: "1010",
   Amount: 245
 }

 {
   desc: "Sum account 101 with 4 digits,
   Amount: 245
  }

 {
    desc: "102",
    Amount: 288
  }

 {
    desc: "1020",
    Amount: 21
  }

 {
    desc: "1021 ",
    Amount: 68
 }

{
    desc: "1022",
    Amount: -87
  }

 {
    desc: "1023 ",
    Amount: -668
 }

{
   desc: "Sum account 102 with 4 digits ",
   Amount: -666
 }

]

I have tried this code but it's not working:

const filtered = newaccount.filter(obj => obj.number.length >3 &&  
 obj.number?.includes(obj.number.slice(0, 3)));

Answer 1

I'm not sure I completely understand your question so I'm going to paraphrase and please correct me if I'm wrong: You have an array of objects, { number: number, amount: number }, and you want to sum the amounts of objects sharing the same first 3 digits in the number field where the length of number is greater than 3 (in other words, account number over 99):

interface AccountBalance {
    number: number,
    amount: number
}

interface AccountSumDescription {
    desc: string,
    sum: number
}

const balances: AccountBalance[] = [
    {number:1, amount: -5425},
    {number:10, amount: 12},
    {number:100, amount: 100},
    {number:1000, amount: -4971},
    {number:1001, amount: 84000},
    {number:1002, amount: 500},
    {number:1002, amount: 6411},
    {number:1010, amount: 245},
    {number:102, amount: 288},
    {number:1020, amount: 21},
    {number:1021, amount: 68},
    {number:1020, amount: -87},
    {number:1032, amount: -668}
];
 
function sumBalancesForAccountNumbersOver99(balances: AccountBalance[]): AccountSumDescription[] {
    const accountSums: Map<string, number> = new Map<string, number>();
    balances.filter(b => b.number > 99).forEach(b => {
        const key: string = b.number.toString().slice(0,3);
        const accountSum = accountSums.get(key);
        accountSums.set(key, (accountSum !== undefined ? accountSum : 0) + b.amount);
    });
    const result: AccountSumDescription[] = [];
    accountSums.forEach((v,k) => result.push({desc: `Sum accounts ${k}*`, sum: v}));
    return result;
}

console.log(sumBalancesForAccountNumbersOver99(balances));

The output should be:

[
  { desc: 'Sum accounts 100*', sum: 86040 },
  { desc: 'Sum accounts 101*', sum: 245 },
  { desc: 'Sum accounts 102*', sum: 290 },
  { desc: 'Sum accounts 103*', sum: -668 }
]