How to merge Array Key value from another Key in JavaScript

Question

[
    0: {employeeId: "2", name: "chandan", email: "chandan@gmail.com"}
    1: {gender: "male"}
]

I want this Array like this:

[
  0: {employeeId: "2", name: "chandan", email: "chandan@gmail.com", gender: "male"}
]

score 2 · Answer 1 · answered Jun 06 '20 at 18:52

2

You can use the spread operator to create a new object, that will copy over the properties of the two existing objects.

arr[0]={...arr[0],...arr[1]};

answered Jun 06 '20 at 18:52

Mark Colby

191
6

Array length is not static So I can't use static [0] the keys is dynamic it would be helpful if you suggest code with dynamic value; – Chandan Rathore Jun 06 '20 at 18:54
So your array has multiple values ? Not only one? – ChrisR Jun 06 '20 at 18:54
Józef Podlecki's answer allows for a non-static array length. – Mark Colby Jun 06 '20 at 19:02

Józef Podlecki · Answer 2 · 2020-06-06T19:07:25.063

2

array.reduce and spread can help you

const arr = [{
    employeeId: "2",
    name: "chandan",
    email: "chandan@gmail.com"
  },
  {
    gender: "male"
  }
]

const result = arr.reduce((acc, obj) => ({
  ...acc,
  ...obj
}), {});

console.log(result);

--Edit

Object.assign flavor ( seems to be 1% slower on chrome 83 though)

const arr = [{
    employeeId: "2",
    name: "chandan",
    email: "chandan@gmail.com"
  },
  {
    gender: "male"
  }
]

const result = arr.reduce((acc, obj) => Object.assign(acc, obj), {});

console.log(result);

edited Jun 06 '20 at 19:07

answered Jun 06 '20 at 18:56

Józef Podlecki

10,453
5
24
50

1

This will do it dynamically, regardless of how many elements are in the array. It loops through the array, spreading the results over and over again. – Mark Colby Jun 06 '20 at 19:01
Now I wonder if `Object.assign` is good alternative to that. Would have to make some tests on jsperf – Józef Podlecki Jun 06 '20 at 19:03
Added variant with object.assign – Józef Podlecki Jun 06 '20 at 19:07
@JózefPodlecki any difference between spread & Object.assign? – Chandan Rathore Jun 06 '20 at 19:13
[Apart from availability between browsers and slight performance there is none](https://stackoverflow.com/questions/32925460/object-spread-vs-object-assign) – Józef Podlecki Jun 06 '20 at 23:04

score 1 · Answer 3 · answered Jun 07 '20 at 04:42

use reduce without initial value will agreggate.

const arr = [
  {
    employeeId: "2",
    name: "chandan",
    email: "chandan@gmail.com",
  },
  {
    gender: "male",
  },
];

const output = arr.reduce((acc, curr) => Object.assign(acc, curr));

console.log(output);

score 0 · Answer 4 · answered Jun 07 '20 at 05:37

You can also do this by mapping it and then taking fromEntries:

var data=[ {employeeId: "2", name: "chandan", email: "chandan@gmail.com"}, {gender: "male"}];

var result = Object.fromEntries(data.flatMap(k=>Object.entries(k)));

console.log(result);

How to merge Array Key value from another Key in JavaScript

4 Answers4