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

Question

There are two arrays:

[
  {\"id\": \"5c5030b9a1ccb11fe8c321f4\", \"quantity\": 1},
  {\"id\": \"344430b94t4t34rwefewfdff\", \"quantity\": 5},
  {\"id\": \"34         


        

Answer 1

You can just do this with reduce:

let a1 = [
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 2},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 1}
];

let a2 = [
  {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 1},
  {"id": "344430b94t4t34rwefewfdff", "quantity": 5},
  {"id": "342343343t4t34rwefewfd53", "quantity": 3}
];

let result = Object.values(a1.concat(a2).reduce((acc, v) => {
   if (!acc[v.id]) {
       acc[v.id] = {id: v.id, quantity: 0};
   }
   acc[v.id].quantity += v.quantity;
   return acc;
}, {}));

console.log("Results: ", result);