Add new attribute (element) to JSON object using JavaScript

Question

How do I add new attribute (element) to JSON object using JavaScript?

Answer 1

JSON stands for JavaScript Object Notation. A JSON object is really a string that has yet to be turned into the object it represents.

To add a property to an existing object in JS you could do the following.

object["property"] = value;

or

object.property = value;

If you provide some extra info like exactly what you need to do in context you might get a more tailored answer.

Answer 2

var jsonObj = {
    members: 
    {
        host: "hostName",
        viewers: 
        {
            user1: "value1",
            user2: "value2",
            user3: "value3"
        }
    }
}

for(var i=4; i<=8; i++){
    var newUser = "user" + i;
    var newValue = "value" + i;
    jsonObj.members.viewers[newUser] = newValue ;

}

console.log(jsonObj);

Answer 3

A JSON object is simply a javascript object, so with Javascript being a prototype based language, all you have to do is address it using the dot notation.

mything.NewField = 'foo';

Answer 4

With ECMAScript since 2015 you can use Spread Syntax ( …three dots):

let  people = { id: 4 ,firstName: 'John'};
people = { ...people, secondName: 'Fogerty'};

It's allow you to add sub objects:

people = { ...people, city: { state: 'California' }};

the result would be:

{  
   "id": 4,
   "firstName": "John",
   "secondName": "Forget",
   "city": {  
      "state": "California"
   }
}

You also can merge objects:

var mergedObj = { ...obj1, ...obj2 };

Answer 5

thanks for this post. I want to add something that can be useful.

For IE, it is good to use

object["property"] = value;

syntax because some special words in IE can give you an error.

An example:

object.class = 'value';

this fails in IE, because "class" is a special word. I spent several hours with this.

Answer 6

You can also use Object.assign from ECMAScript 2015. It also allows you to add nested attributes at once. E.g.:

const myObject = {};

Object.assign(myObject, {
    firstNewAttribute: {
        nestedAttribute: 'woohoo!'
    }
});

Ps: This will not override the existing object with the assigned attributes. Instead they'll be added. However if you assign a value to an existing attribute then it would be overridden.

Answer 7

extend: function(){
    if(arguments.length === 0){ return; }
    var x = arguments.length === 1 ? this : arguments[0];
    var y;

    for(var i = 1, len = arguments.length; i < len; i++) {
        y = arguments[i];
        for(var key in y){
            if(!(y[key] instanceof Function)){
                x[key] = y[key];
            }
        }           
    };

    return x;
}

Extends multiple json objects (ignores functions):

extend({obj: 'hej'}, {obj2: 'helo'}, {obj3: {objinside: 'yes'}});

Will result in a single json object

Answer 8

You can also dynamically add attributes with variables directly in an object literal.

const amountAttribute = 'amount';
const foo = {
                [amountAttribute]: 1
            };
foo[amountAttribute + "__more"] = 2;

Results in:

{
    amount: 1, 
    amount__more: 2
}

Answer 9

You can also add new json objects into your json, using the extend function,

var newJson = $.extend({}, {my:"json"}, {other:"json"});
// result -> {my: "json", other: "json"}

A very good option for the extend function is the recursive merge. Just add the true value as the first parameter (read the documentation for more options). Example,

var newJson = $.extend(true, {}, {
    my:"json",
    nestedJson: {a1:1, a2:2}
}, {
    other:"json",
    nestedJson: {b1:1, b2:2}
});
// result -> {my: "json", other: "json", nestedJson: {a1:1, a2:2, b1:1, b2:2}}

Answer 10

Uses $.extend() of jquery, like this:

token = {_token:window.Laravel.csrfToken};
data = {v1:'asdass',v2:'sdfsdf'}
dat = $.extend(token,data); 

I hope you serve them.

Answer 11

Following worked for me for add a new field named 'id'. Angular Slickgrid usually needs such id

  addId() {
     this.apiData.forEach((item, index) => {
     item.id = index+1;
  });