unique_arrays_of_object.js

// Merging two arrays of objects
// if the object is same in both arrays, then update the quantity else add the object to the new merged array array

const arr1 = [
   // from db
   { name: 'orange', qty: 5, vendor_details: { name: 'akash', vendor_id: 8 } },
   { name: 'apple', qty: 10, vendor_details: { name: 'akash', vendor_id: 8 } },
   { name: 'mango', qty: 15, vendor_details: { name: 'akash', vendor_id: 8 } },
];

const arr2 = [
   //  local storage
   { name: 'orange', qty: 3, vendor_details: { name: 'akash', vendor_id: 8 } },
   { name: 'apple', qty: 8, vendor_details: { name: 'akash', vendor_id: 8 } },
   { name: 'banana', qty: 12, vendor_details: { name: 'akash', vendor_id: 8 } },
];

const combined = [...arr1, ...arr2];

let tracker = [],
   merged = [],
   length = combined.length;

for (let i = 0; i < length; i++) {
   if (tracker[combined[i].name]) {
      merged.find((item) => item.name === combined[i].name).qty +=
         combined[i].qty;
      continue;
   }
   tracker[combined[i].name] = true;
   merged.push(combined[i]);
}