How to dynamically add object inside json array?

Question

I'm trying to dynamically add an object inside every object which is present in my json array. But I'm unable to do so. My object is getting appended at the end of json which is not what I want.

jsonArray:any=[
    {
        "id": 1000,
        "body": "some comment",
        "postId": 1
    },
    {
        "id": 2,
        "body": "some comment",
        "postId": 1
    },
    {
        "id": 3,
        "body": "some comment",
        "postId": 1
    }
]

selectFLag:any={"selected":"true"}

temArray:any;

learnJSONPArse()
{
    for (var i = 0; this.jsonArray.length > i; i++) 
    {
        Alert(this.jsonArray.length)
    }
}

this.jsonArray.push(this.selectFLag)

-----expected output is

[
    {
        "id": 1000,
        "body": "some comment",
        "postId": 1,
        "selected":"true"
    },
    {
        "id": 2,
        "body": "some comment",
        "postId": 1,
        "selected":"true"
    },
    {
        "id": 3,
        "body": "some comment",
        "postId": 1,
        "selected":"true"
    }
]

Possible duplicate of [Add new attribute (element) to JSON object using JavaScript](https://stackoverflow.com/questions/736590/add-new-attribute-element-to-json-object-using-javascript) — computercarguy, Aug 01 '19 at 18:48
Please show a minimal reproduction of the issue you are having with desired input and output. — Keenan Diggs, Aug 01 '19 at 18:58
@KeenanDiggs desired input [ { "id": 1000, "body": "some comment", "postId": 1 }, { "id": 2, "body": "some comment", "postId": 1 }, { "id": 3, "body": "some comment", "postId": 1 } ] — anonymous, Aug 01 '19 at 19:04
@KeenanDiggs desired output [ { "id": 1000, "body": "some comment", "postId": 1, "selected":"true" }, { "id": 2, "body": "some comment", "postId": 1, "selected":"true" }, { "id": 3, "body": "some comment", "postId": 1, "selected":"true" } ] — anonymous, Aug 01 '19 at 19:05

Keenan Diggs · Answer 1 · 2019-08-01T19:14:55.900

You're question is a little unclear, but it sounds like you want to map each item in your array to a new item. The new item is the same as the old one, but assigned an additional property.

If so, something like this could work for you:

const objToAppend = { selected: true };
jsonArray.map(item => Object.assign(item, objToAppend));

Refs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

How to dynamically add object inside json array?

1 Answers1