Concatenate two JSON objects

Question

I have two JSON objects with the same structure and I want to concat them together using Javascript. Is there an easy way to do this?

How exactly do you want to concat them? Each element of both objects or both objects as a new object having the origin objects as elements or …? — Gumbo
– Gumbo, Commented Jan 11, 2009 at 20:33
Basically I have an array of 10 Json objects. I then make an Ajax call to get another 10 Json objects and I want to concat them together to create an array of 20 objects. — Craig
– Craig, Commented Jan 11, 2009 at 21:04
Do you have JSON objects (deserialized into a variable of type Object) or strings (serialized form)? — Ateş Göral
– Ateş Göral, Commented Jan 14, 2009 at 16:47

0stone0 · Accepted Answer · 2024-10-10 14:59:30Z

121

Based on your description in the comments, you'd simply do an array concat():

var jsonArray1 = [{'name': "doug", 'id':5}, {'name': "dofug", 'id':23}];
var jsonArray2 = [{'name': "goud", 'id':1}, {'name': "doaaug", 'id':52}];

jsonArray1 = jsonArray1.concat(jsonArray2);

console.log(jsonArray1)
// [{'name': "doug", 'id':5}, {'name': "dofug", 'id':23}, {'name': "goud", 'id':1}, {'name': "doaaug", 'id':52}];

edited Oct 10, 2024 at 14:59

0stone0

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answered Jan 12, 2009 at 0:07

jacobangel

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3 Comments

Breton Over a year ago

Your assumption about the value of jsonArray1 is incorrect. concat doesn't modify the original array, it returns a new array.

Breton Over a year ago

You'd need to do jsonArray1 = jsonArray1.concat(jsonArray2);

Kevinleary.net Over a year ago

For the 1, 2, 3 this can be handy for a clean merge: var arr3 = [].concat(arr1, arr2);

BuZZ-dEE · Accepted Answer · 2024-10-10 14:44:57Z

55

The actual way is using JS Object.assign.

Object.assign(target, ...sources)

MDN Link

There is another object spread operator which is proposed for ES7 and can be used with Babel plugins.

 Obj = {...sourceObj1, ...sourceObj2}

edited Oct 10, 2024 at 14:44

BuZZ-dEE

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answered Jun 24, 2017 at 8:26

Raunaq Sachdev

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Comments

Community · Accepted Answer · 2018-09-14 11:17:06Z

47

If you'd rather copy the properties:

var json1 = { value1: '1', value2: '2' };
var json2 = { value2: '4', value3: '3' };


function jsonConcat(o1, o2) {
 for (var key in o2) {
  o1[key] = o2[key];
 }
 return o1;
}

var output = {};
output = jsonConcat(output, json1);
output = jsonConcat(output, json2);

Output of above code is{ value1: '1', value2: '4', value3: '3' }

edited Sep 14, 2018 at 11:17

CommunityBot

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answered Jan 11, 2009 at 20:50

user53964

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2 Comments

pauldcomanici Over a year ago

As they are objects, you don't need to return it, as objects are passed by reference

Rodinga Over a year ago

Had an interesting corner case where I needed to merge properties from two JSON objects, this worked like a charm. Thanks.

Arsen Khachaturyan · Accepted Answer · 2020-01-14 14:31:11Z

41

I use:

let x = { a: 1, b: 2, c: 3 }

let y = {c: 4, d: 5, e: 6 }

let z = Object.assign(x, y)

console.log(z)

// OUTPUTS:
{ a:1, b:2, c:4, d:5, e:6 }

From here.

edited Jan 14, 2020 at 14:31

Arsen Khachaturyan

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answered Sep 10, 2018 at 23:16

Alvaro

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Comments

tnimas · Accepted Answer · 2015-03-24 16:17:34Z

27

You can use jquery extend method.

Example:

o1 = {"foo":"bar", "data":{"id":"1"}};
o2 = {"x":"y"};
sum = $.extend(o1, o2);

Result:

sum = {"foo":"bar", "data":{"id":"1"}, "x":"y"}

answered Mar 24, 2015 at 16:17

tnimas

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3 Comments

Rijo Over a year ago

Better solution

fsinisi90 Over a year ago

Simpler and cleaner solution.

BritishWerewolf Over a year ago

A case where jQuery isn't overkill.

tushar · Accepted Answer · 2019-06-14 07:55:40Z

21

if using TypeScript, you can use the spread operator (...)

var json = {...json1,...json2}

answered Jun 14, 2019 at 7:55

tushar

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1 Comment

CrsCaballero Over a year ago

Thank you!, for some reason, this have worked better on react, to use with render states

Soviut · Accepted Answer · 2009-01-11 20:40:33Z

18

One solution is to use a list/array:

var first_json = {"name":"joe", "age":27};
var second_json = {"name":"james", "age":32};

var jsons = new Array();
jsons.push(first_json);
jsons.push(second_json);

Result

jsons = [
    {"name":"joe", "age":27},
    {"name":"james", "age":32}
]

answered Jan 11, 2009 at 20:40

Soviut

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2 Comments

PascalVKooten Over a year ago

Cough, what about [first_json, second_json]?

Soviut Over a year ago

That's certainly correct if the OP has has only two objects, but since they specifically mentioned concatenation, it seemed more likely this was a contrived example looking for a way to append.

J.C. Gras · Accepted Answer · 2018-07-03 18:00:27Z

12

You can use Object.assign() method. The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.[1]

var o1 = { a: 1 }, o2 = { b: 2 }, o3 = { c: 3 };

var obj = Object.assign(o1, o2, o3);
console.log(obj); // { a: 1, b: 2, c: 3 }

answered Jul 3, 2018 at 18:00

J.C. Gras

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2 Comments

Akash Agarwal Over a year ago

Best, concise code with a relevant example so far! It would be nice if you clarify what happens when the keys are not unique across different objects :)

AbhiNickz Over a year ago

if o1, o2, contains the same keys, the right one is assigned to the obj. JSON.stringify(Object.assign({ "test": 1 }, { "test": 2 }, { "test": 3 }, { "test2": 4 } )); => '{"test":3,"test2":4}'

Breton · Accepted Answer · 2009-01-11 21:24:20Z

6

okay, you can do this in one line of code. you'll need json2.js for this (you probably already have.). the two json objects here are unparsed strings.

json1 = '[{"foo":"bar"},{"bar":"foo"},{"name":"craig"}]';

json2 = '[{"foo":"baz"},{"bar":"fob"},{"name":"george"}]';

concattedjson = JSON.stringify(JSON.parse(json1).concat(JSON.parse(json2)));

answered Jan 11, 2009 at 21:24

Breton

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Comments

Rejayi CS · Accepted Answer · 2015-12-08 12:51:24Z

2

Just try this, using underscore

var json1 = [{ value1: '1', value2: '2' },{ value1: '3', value2: '4' }];
var json2 = [{ value3: 'a', value4: 'b' },{ value3: 'c', value4: 'd' }];
var resultArray = [];
json1.forEach(function(obj, index){
  resultArray.push(_.extend(obj,  json2[index]));
});

console.log("Result Array", resultArray);

Result

answered Dec 8, 2015 at 12:51

Rejayi CS

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Comments

Luca Matteis · Accepted Answer · 2009-01-12 05:05:57Z

1

var baseArrayOfJsonObjects = [{},{}];
for (var i=0; i<arrayOfJsonObjectsFromAjax.length; i++) {
    baseArrayOfJsonObjects.push(arrayOfJsonObjectsFromAjax[i]);
}

answered Jan 12, 2009 at 5:05

Luca Matteis

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Comments

Stephen Rauch · Accepted Answer · 2018-11-11 03:49:35Z

1

I use:

let jsonFile = {};    
let schemaJson = {};    
schemaJson["properties"] = {};    
schemaJson["properties"]["key"] = "value";
jsonFile.concat(schemaJson);

edited Nov 11, 2018 at 3:49

Stephen Rauch♦

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answered Nov 11, 2018 at 3:21

Alvaro

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Comments

Thiago · Accepted Answer · 2021-10-02 23:49:28Z

1

The simplest way :

const json1 = { value1: '1', value2: '2' };
const json2 = { value2: '4', value3: '3' };

const combinedData = {
  json1,
  json2
};

console.log(combinedData)

answered Oct 2, 2021 at 23:49

Thiago

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Comments

Frederick Montiel · Accepted Answer · 2022-07-05 16:05:51Z

I dont know if you want this:

U can use this for create from arrays, all arrays need contains the same number of elments.

Example: If you have:

let a = ["a", "b", "c"];
let b = [1, 2, 3];

Use

concatArraysLikeJson([a, b]);

The result of is:

let result = {
 0 : ["a", 1],
 1 : ["b", 2],
 2 : ["c", 3]
};

Typescript

concatArraysLikeJson(arrays:any){
 let result:any = {};

 let size:number = 0;
 let make:boolean = true;

 if(arrays.length > 0){
  size = arrays[0].length;

  for(let i = 1; i < arrays.length; i++){
    let array = arrays[i];
    
    if(make){
      if(array.length != size){
        make = false;
      }
    }
  }
 }

 if(make){
  for (let o = 0; o < size; o++) {
    result[o] = [];
  }

  for(let i = 0; i < arrays.length; i++){
    const array = arrays[i];

    //console.log(array);

    for (let o = 0; o < size; o++) {
      const element = array[o];
      result[o].push(element);
    }
  }

  return result;
 }else{
  return false;
 }
}

Javascript:

concatArraysLikeJson(arrays){
 let result = {};

 let size = 0;
 let make = true;

 if(arrays.length > 0){
  size = arrays[0].length;

  for(let i = 1; i < arrays.length; i++){
    let array = arrays[i];
    
    if(make){
      if(array.length != size){
        make = false;
      }
    }
  }
}

if(make){
  for (let o = 0; o < size; o++) {
    result[o] = [];
  }

  for(let i = 0; i < arrays.length; i++){
    const array = arrays[i];

    //console.log(array);

    for (let o = 0; o < size; o++) {
      const element = array[o];
      result[o].push(element);
    }
  }

  return result;
}else{
  return false;
}
  }

Raaghu · Accepted Answer · 2022-12-26 14:28:20Z

The JSON Objects and Arrays can be combined in multiple ways within a structure

I can merge json with rules using json-object-merge

import JSONObjectMerge from "json-object-merge";

const target = {
  store: {
    book: [
      {
        category: "reference",
        author: "Nigel Rees",
        title: "Sayings of the Century",
        price: 8.95
      }
    ],
    bicycle: {
      color: "red",
      price: 19.95
    }
  }
};

const source = {
  store: {
    book: [
      {
        category: "fiction",
        author: "Evelyn Waugh",
        title: "Sword of Honour",
        isbn: "0-679-43136-5",
        price: 12.99
      }
    ]
  }
};
const merged = JSONObjectMerge(target, source, { "$.store.book": "PREPEND" });

expect(merged).toEqual({
  store: {
    book: [
      {
        // books from source are prepended to the original array
        category: "fiction",
        author: "Evelyn Waugh",
        title: "Sword of Honour",
        isbn: "0-679-43136-5",
        price: 12.99
      },
      {
        category: "reference",
        author: "Nigel Rees",
        title: "Sayings of the Century",
        price: 8.95
      }
    ],
    bicycle: {
      color: "red",
      price: 19.95
    }
  }
});

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