CODEWITHSUNDEEP
javascriptarraysobjectarray-merge
Ngô Tâm
Ngô Tâm

Reputation: 15

How to merge duplicate object parent items in array?

I want to merge objects in array so that objects with the same id (which is a child object) can sum the total_price and total_quantity values. Here is my data array:

var data = [
        {
            "_id": {
                "month": 5,
                "year": 2021
            },
            "total_price": 145111500,
            "total_quantity": 7
        },
        {
            "_id": {
                "month": 6,
                "year": 2021
            },
            "total_price": 98386000,
            "total_quantity": 5
        },
        {
            "_id": {
                "month": 6,
                "year": 2021
            },
            "total_price": 32500000,
            "total_quantity": 3
        }
    ]

I want to merge objects that have the duplicate "_id". Here is the output result:

var merge = [
        {
            "_id": {
                "month": 5,
                "year": 2021
            },
            "total_price": 145111500,
            "total_quantity": 7
        },
        {
            "_id": {
                "month": 6,
                "year": 2021
            },
            "total_price": 130886000,
            "total_quantity": 8
        }
    ]

Thanks in advance.

Upvotes: 1

Views: 288

Answers (2)

Ares Stavropoulos
Ares Stavropoulos

Reputation: 170

var ids = [];
var merge =  [];
for (let i = 0; i < data.length; i++) {
  obj = data[i];
  let dupId = false;
  for (let j = 0; j < ids.length; j++) {
    if (ids[j]["month"] == obj["_id"]["month"] && ids[j]["year"] == obj["_id"]["year"]) {
      merge[j]["total_price"] += obj["total_price"];
      merge[j]["total_quantity"] += obj["total_quantity"];
      dupId = true;
      break;
    }
  }
  if (!dupId) {
    ids.push(obj["_id"]);
    merge.push(obj);
  }
}

The code will:

  • Declare and initialize merge array to an empty array
  • Loop through all elements from data array
  • And inside, check for duplicate of element in merge array
  • If found, add total quantities and total prices
  • If not found, add element to merge array

Upvotes: 1

Majed Badawi
Majed Badawi

Reputation: 28414

const data = [
  { "_id": { "month": 5, "year": 2021 }, "total_price": 145111500, "total_quantity": 7 },
  { "_id": { "month": 6, "year": 2021 }, "total_price": 98386000, "total_quantity": 5 },
  { "_id": { "month": 6, "year": 2021 }, "total_price": 32500000, "total_quantity": 3 }
];

const res = [...
  // iterate over the list
  data.reduce((map, item) => {
    // construct key from _id
    const key = `${item._id.month}-${item._id.year}`;
    // get prev map value of key if exists
    const prev = map.get(key);
    // update map, if prev not found, set value as item, or update it with the added values
    map.set(
      key, 
      !prev 
        ? item 
        : { ...item, total_price: prev.total_price + item.total_price, total_quantity: prev.total_quantity + item.total_quantity }
    );
    return map;
  }, new Map)
  // return map values
  .values()
];

console.log(res);

Upvotes: 1

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