How I can merge two arrays objects

Question

I need merge two arrays of objects, and no duplicates, with es6 syntax. In my task few more keys in objects.

But I think this is not problem. In array2 always objects that are contained inside array1

Here is the array

array1 = [
   {name: 'one', count: 0}, 
   {name: 'two', count: 0}, 
   {name: 'three', count: 0},
   {name: 'four', count: 0} 
]

array2 = [
   {name: 'two', count: 4},
   {name: 'four', count: 2}
]

I need get this:

array3 = [
  {name: 'one', count: 0},
  {name: 'two', count: 4},
  {name: 'three', count: 0},
  {name: 'four', count: 2}
]

We can guide you or unblock you, but you have to make an attempt first. Please show what you've tried so far. — Jeremy Thille, Jan 21 '19 at 13:28
[enter link description here](https://stackoverflow.com/questions/7146217/merge-2-arrays-of-objects) Try solutions on this link. — monofal, Jan 21 '19 at 13:30
if in array1 you have an tem with count 1 for example, and in the array 2 you have the same item with count 2, what will be the count value of the item included in the final array? — quirimmo, Jan 21 '19 at 13:33
Possible duplicate of [Merge 2 arrays of objects](https://stackoverflow.com/questions/7146217/merge-2-arrays-of-objects) — Ritul Lakhtariya, Jan 21 '19 at 13:33

score 1 · Answer 1 · answered Jan 21 '19 at 13:30

const array1 = [
  {name: 'one', count: 0}, 
  {name: 'two', count: 0}, 
  {name: 'three', count: 0},
  {name: 'four', count: 0} 
]
const array2 = [
  {name: 'two', count: 4},
  {name: 'four', count: 2}
]

const result = array1.map(a => {
  const b = array2.find(b => b.name === a.name);
  if (b) {
    return {name: a.name, count: a.count + b.count}
  }
  return a;
});

console.log(result);

score 0 · Answer 2 · answered Jan 21 '19 at 13:31

let all = array1.concat(array2)
//avoid dupplicates by  key
let map = all.reduce((acc,item)=>{acc[item.name] = item; return acc;},{});
//convert map back to array
let array3 = Object.values(map)
console.log(array3);
//
[ { name: 'one', count: 0 },
  { name: 'two', count: 4 },
  { name: 'three', count: 0 },
  { name: 'four', count: 2 } ]

Kaddath · Answer 3 · 2019-01-21T14:22:00.897

map can be used to call a function on each element of an array. The main difference with the version using find is that it will go through all elements of array2, so that if you have 2 elements with name: 'two' in the array, both of them will increment the count. With find only the fist found will add.

const array1 = [
  {name: 'one', count: 0}, 
  {name: 'two', count: 0}, 
  {name: 'three', count: 0},
  {name: 'four', count: 0} 
  ],
  array2 = [
  {name: 'two', count: 4},
  {name: 'four', count: 2}
  ];

const array3 = array1.map(obj => {
  let _count = obj.count;
  array2.forEach(obj2 => {
    if(obj2.name === obj.name){
      _count += obj2.count;
    }
  });
  return { name: obj.name, count: _count };
});
    
console.log(array3);

EDIT: modified following @HMR suggestion (thanks pointing my mistake) + used forEach on array2 because i don't use any returned array

map should not be used to mutate the array it's used on. Better to use forEach instead or return a new object. — HMR, Jan 21 '19 at 14:09

How I can merge two arrays objects

3 Answers3