Using map to change object's properties of an array of objects

Question

I have an object that has the key ID and some status key. I wanna count how many times the same status repeats itself. My object will look like this

const items = { id: 2, status_a: 1, status_b: 1, status_c: 3 };

This is my code

curr.userBuyer is a number. curr.status is a string, for each equal status, i want to add 1 to it

const userBuyers: any[] = buyers.reduce((acc: any[], curr) => {
    if (acc.filter((item) => item.id == curr.userBuyer).length == 0) {
      //If the there's no item in acc, then it gets pushed into it
      acc.push({ id: curr.userBuyer, [curr.status]: 1 });

      return acc;
    } else {
      //If acc already have that item
      acc = acc.map((retail) => {
        //Check if that key already exists
        const isKey = retail[curr.status] ? true : false;

        //If the key exists, then it will add 1 to the existing value, else it will set it as 1
        return { ...retail, [curr.status]: isKey ? retail[curr.status]++ : 1 };
      });

      return acc;
    }
  }, []);

This is what is returning

 [
    {
      id: 713,
      delivered: 1,
      sold: 1,
      in_delivery: 1,
    },
    {
      id: 833,
      delivered: 1,
      sold: 1,
      in_delivery: 1,
    },
  ];

It's not adding 1 to the status that already exists.

What am i doing wrong?

retail[curr.status]++ should be ++retail[curr.status] or retail[curr.status]+1 — Charchit Kapoor
– Charchit Kapoor, Commented Oct 3, 2022 at 17:12
For some reason both id's are receiving equal values, like both of them have delivered: 9, sold: 2, in_delivery: 1. It should be different — José Carlos
– José Carlos, Commented Oct 3, 2022 at 17:56

Charchit Kapoor · Accepted Answer · 2022-10-04 04:20:12Z

1

You have two errors:

You are using the postfix operator to increment count retail[curr.status]++, instead, use the prefix operator ++retail[curr.status] or simply (retail[curr.status] + 1).
You are updating all the items, in an account, only the matching item should be updated.

Try this:

const userBuyers: any[] = buyers.reduce((acc: any[], curr) => {
    if (acc.filter((item) => item.id == curr.userBuyer).length == 0) {
      acc.push({ id: curr.userBuyer, [curr.status]: 1 });
      return acc;
    } else {
      acc = acc.map((retail) => {
        if (retail.id  === curr.userBuyer) {
          const isKey = retail[curr.status] ? true : false;
          return { ...retail, [curr.status]: isKey ? retail[curr.status] + 1 : 1 };
        }
        return retail;
      });
      return acc;
    }
  }, []);

answered Oct 4, 2022 at 4:20

Charchit Kapoor

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1 Comment

José Carlos Over a year ago

Yes, it took me a bit to realize i was updating everything hahaha. Thanks!

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