Map an array by value

Question

I have an array of objects, which I want to sum by condition.

[{amount:100, prefix:'a'},{amount:50, prefix:'b'},{amount:70, prefix:'a'},{amount:100, prefix:'b'}]

Is there is a way to map the values, such as I will have two sums, one is 170, of prefix 'a', and one of 150 of prefix 'b'?

@Kektuto Assuming I have an array, I'd like to sum it, by the value of each prefix. The sum of all amounts with prefix 'a' are 170, 100+70 , and the sum of all amounts with prefix 'b' are 150, as there are two objects with the prefix 'b', one has amount of 100, and the other has amount of 50 — user3150947
– user3150947, Commented Nov 2, 2021 at 14:21

Ali Baykal · Accepted Answer · 2021-11-02 14:24:27Z

4

const result = [{amount:100, prefix:'a'},{amount:50, prefix:'b'},{amount:70, prefix:'a'},{amount:100, prefix:'b'}].reduce(
  (acc, {amount, prefix}) => {
    return {
      ...acc,
      [prefix]: acc[prefix] + amount
    }
   
  }, {a: 0, b: 0}
);


console.log(result)

answered Nov 2, 2021 at 14:24

Ali Baykal

3242 silver badges5 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Johnathan DiMatteo · Accepted Answer · 2021-11-02 14:43:08Z

2

function compute_sums(acc, curr) {
    if (acc[curr['prefix']]) {
        acc[curr['prefix']] += curr['amount']
    } else {
       acc[curr['prefix']] = curr['amount']
   }
   return acc;
}
const arr = [{amount:100, prefix:'c'}, {amount:100, prefix:'a'},{amount:50, prefix:'b'},{amount:70, prefix:'a'},{amount:100, prefix:'b'}];
const answer = arr.reduce(compute_sums, {});
console.log(answer);

Similar answer to Ali, but mine will compute the sums for any prefix, not just a and b.

edited Nov 2, 2021 at 14:43

answered Nov 2, 2021 at 14:35

Johnathan DiMatteo

513 bronze badges

Collectives™ on Stack Overflow

Map an array by value

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related