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How to merge two arrays and sum values of duplicate objects using lodash

There are two arrays:

[
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 1},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 5},
  {"id": "342343343t4t34rwefewfd53", "quantity": 3}
]

and

[
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 2},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 1}
]

How to combine them into one summing quantity?

[
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 3},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 6},
  {"id": "342343343t4t34rwefewfd53", "quantity": 3}
]

One of them can be empty sometimes

like image 730
Sgt Maddonut Avatar asked Feb 26 '19 11:02

Sgt Maddonut


People also ask

How do I merge two arrays in Lodash?

If both arrays are in the correct order; where each item corresponds to its associated member identifier then you can simply use. var merge = _. merge(arr1, arr2);

How do I merge two objects in Lodash?

The _. merge() method is used to merge two or more objects starting with the left-most to the right-most to create a parent mapping object. When two keys are the same, the generated object will have value for the rightmost key.


1 Answers

You can do it with plain JavaScript.

Use Array.reduce() to make an intermediate dictionary by id and accumulate the quantities, then turn it into an array with Object.values():

const arr1 = [
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 1},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 5},
  {"id": "342343343t4t34rwefewfd53", "quantity": 3}
];
const arr2 = [
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 2},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 1}
];

const result = Object.values([...arr1, ...arr2].reduce((acc, { id, quantity }) => {
  acc[id] = { id, quantity: (acc[id] ? acc[id].quantity : 0) + quantity  };
  return acc;
}, {}));

console.log(result);
like image 146
jo_va Avatar answered Sep 18 '22 22:09

jo_va