Is there a way to merge two nested array based on common key [closed]

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This are the two array that needs merging based on common id, the nested array should also be merged

First Array

const arr1 = [
    { id: 1, name: "sai", accounts: ["a"] },
    { id: 2, name: "King", accounts:[] },
    { id: 3, name: "Queen", accounts:["c"] },
    { id: 4, name: "kai", accounts:["e"] },
  ];

Second Array

const arr2 = [
    { id: 1, age: 23, accounts: ["b"] },
    { id: 2, age: 24, accounts:[] },
    { id: 3, age: 25, accounts:["d"] }
  ];

Output should be

[  
  { id: 1, age: 23, name:"sai", accounts: ["a","b"] },
  { id: 2, age: 24, name: "King", accounts:[] },
  { id: 3, age: 25, name:"Queen", accounts:["c","d"] },
  { id: 4, name: "kai", accounts:["e"] },
]

Please edit the question to show your own efforts at solving this, because Stack Overflow is not a write-my-code-for-me service. Also please see How to Ask. — Peter B
– Peter B, Commented Sep 16, 2022 at 9:54

Mariusz Malek · Accepted Answer · 2022-09-16 10:20:19Z

1

This should work:

const arr1 = [
    { id: 1, name: "sai", accounts: ["a"] },
    { id: 2, name: "King", accounts:[] },
    { id: 3, name: "Queen", accounts:["c"] },
    { id: 4, name: "kai", accounts:["e"] },
];

const arr2 = [
    { id: 1, age: 23, accounts: ["b"] },
    { id: 2, age: 24, accounts:[] },
    { id: 3, age: 25, accounts:["d"] }
];

const result = arr1.map((item, i) => Object.assign({}, item, arr2[i]));

New version:

const mergeArrays = () => {
   let res = [];
   
   for (var i = 0; i < arr1.length; i++) {
       let item = arr1[i];
       
       if (arr2[i] && arr1[i].id == arr2[i].id) {
            item.age = arr2[i].age;
            item.accounts = item.accounts.concat(arr2[i].accounts);
       }
       
       res.push(item);
   }
   
   return res;
};

edited Sep 16, 2022 at 10:20

answered Sep 16, 2022 at 9:54

Mariusz Malek

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4 Comments

sevack Over a year ago

Thank you for the quick answer. However, Your answer did merge the array but it didn't merge accounts array inside of array.

Peter B Over a year ago

This does not seem to merge accounts. Also it assumes the indexes are the same, but the question asks for a merge based on id.

sevack Over a year ago

This is exactly what I was looking for, thank you for the new version.

Peter B Over a year ago

The updated code assumes that every id that exists in both arrays will be found at the same index in both arrays. That may be true for the example data, but if something changes in the data then that assumption may be invalidated, and this code will break.

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