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Merge two array of objects based on a key

I have two arrays:

Array 1:

[
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" }
]

and array 2:

[
  { id: "abdc4051", name: "ab" },
  { id: "abdc4052", name: "abc" }
]

I need to merge these two arrays based on id and get this:

[
  { id: "abdc4051", date: "2017-01-24", name: "ab" },
  { id: "abdc4052", date: "2017-01-22", name: "abc" }
]

How can I do this without iterating trough Object.keys?

over 4 years ago · Santiago Trujillo
3 answers
Answer question

0

You can do it like this -

let arr1 = [
    { id: "abdc4051", date: "2017-01-24" },
    { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
    { id: "abdc4051", name: "ab" },
    { id: "abdc4052", name: "abc" }
];

let arr3 = arr1.map((item, i) => Object.assign({}, item, arr2[i]));

console.log(arr3);


Use below code if arr1 and arr2 are in a different order:

let arr1 = [
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
  { id: "abdc4051", name: "ab" },
  { id: "abdc4052", name: "abc" }
];

let merged = [];

for(let i=0; i<arr1.length; i++) {
  merged.push({
   ...arr1[i], 
   ...(arr2.find((itmInner) => itmInner.id === arr1[i].id))}
  );
}

console.log(merged);

Use this if arr1 and arr2 are in a same order

let arr1 = [
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
  { id: "abdc4051", name: "ab" },
  { id: "abdc4052", name: "abc" }
];

let merged = [];

for(let i=0; i<arr1.length; i++) {
  merged.push({
   ...arr1[i], 
   ...arr2[i]
  });
}

console.log(merged);

over 4 years ago · Santiago Trujillo Report

0

You can do this in one line

let arr1 = [
    { id: "abdc4051", date: "2017-01-24" },
    { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
    { id: "abdc4051", name: "ab" },
    { id: "abdc4052", name: "abc" }
];

const mergeById = (a1, a2) =>
    a1.map(itm => ({
        ...a2.find((item) => (item.id === itm.id) && item),
        ...itm
    }));

console.log(mergeById(arr1, arr2));

  1. Map over array1
  2. Search through array2 for array1.id
  3. If you find it ...spread the result of array2 into array1

The final array will only contain id's that match from both arrays

over 4 years ago · Santiago Trujillo Report

0

This solution is applicable even when the merged arrays have different sizes. Also, even if the matching keys have different names.

Merge the two arrays by using a Map as follows:

const arr1 = [
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" },
  { id: "abdc4053", date: "2017-01-22" }
];
const arr2 = [
  { nameId: "abdc4051", name: "ab" },
  { nameId: "abdc4052", name: "abc" }
];

const map = new Map();
arr1.forEach(item => map.set(item.id, item));
arr2.forEach(item => map.set(item.nameId, {...map.get(item.nameId), ...item}));
const mergedArr = Array.from(map.values());

console.log(JSON.stringify(mergedArr));
.as-console-wrapper { max-height: 100% !important; top: 0; }

Run the stack snippet to see the result:

[
  {
    "id": "abdc4051",
    "date": "2017-01-24",
    "nameId": "abdc4051",
    "name": "ab"
  },
  {
    "id": "abdc4052",
    "date": "2017-01-22",
    "nameId": "abdc4052",
    "name": "abc"
  },
  {
    "id": "abdc4053",
    "date": "2017-01-22"
  }
]
over 4 years ago · Santiago Trujillo Report
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