Appending to a JS object that is not an array?

Question

I have an object that looks something like this

{
  "_id": "DEADBEEF",
  "_rev": "2-FEEDME",
  "name": "Jimmy Strawson",
  "link": "placeholder.txt",
  "entries": {
    "Foo": 0
  }
}

Which is read into my javascript with a $.getJSON call.

So I have the JS object "reply" that holds all this data.

I need to append items such that "entries" becomes extended as follows:

{
  "_id": "DEADBEEF",
  "_rev": "2-FEEDME",
  "name": "Jimmy Strawson",
  "link": "placeholder.txt",
  "entries": {
    "Foo": 0,
    "Bar": 30,
    "Baz": 4
  }
}

I have tried

reply['entries'].push({"Bar": 0});

But that does not work (I presume because nothing is an array)

Can someone provide an alternative method?

`reply.entries.Bar = 0;` PS: `reply` is a JS object not a JSON. — zerkms, Oct 13 '16 at 04:18
JSON object can't look like that. It's an intrinsic object in JavaScript engines. — Teemu, Oct 13 '16 at 04:20
Thank you @zerkms!! Now if "Bar" has to be a string, like "Bar Baz" what should I do? Sorry. I am new to javascript! — Hubert S. Cumberdale, Oct 13 '16 at 04:21
Let's not bang on too long with all this JSON / object literal debate. We all know what OP means. OP, please read this ~ http://benalman.com/news/2010/03/theres-no-such-thing-as-a-json/ — Phil, Oct 13 '16 at 04:22
Adeneo, I am not stupid... I want to do this reply.entries."string with spaces"= 420; thanks phil! — Hubert S. Cumberdale, Oct 13 '16 at 04:23
@Phil - because it's so easy to create keys without strange characters that would require brackets. I'd even go so far as to replace spaces with underscores to avoid them, however they are valid and it does work. — adeneo, Oct 13 '16 at 04:32
@Phil The terminology is important in some degree, at least the JSON tag should not be polluted with questions like this. — Teemu, Oct 13 '16 at 05:43
@Teemu don't see why you edited the question. OP had fixed it already (*ed:* ah, didn't see it had been ruined by another user) — Phil, Oct 13 '16 at 05:51
@Phil "Removed irrelevant references to JSON", including the JSON tag. — Teemu, Oct 13 '16 at 05:53

score 5 · Answer 1 · edited Jun 20 '20 at 09:12

5

With ES2017 you could use:

const input = (
  { _id: 'DEADBEEF'
  , _rev: '2-FEEDME'
  , name: 'Jimmy Strawson'
  , link: 'placeholder.txt'
  , entries: (
      { Foo: 0
      }
    )
  }
)
 
const output = (
  { ...input
  , entries: (
      { ...input.entries
      , Bar: 30
      , Baz: 4
      }
    )
  }
)

console.info(JSON.stringify(output, null, 2))

Note: this will not mutate the original input object, but instead return a new one (typically a good thing).

edited Jun 20 '20 at 09:12

Community

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1

answered Oct 13 '16 at 04:42

cchamberlain

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That's a great point regarding immutability of the original data. I'd make that text larger :) – Phil Oct 13 '16 at 04:51

Phil · Answer 2 · 2016-10-13T04:34:34.293

4

Here's one more because why not ~ meet Object.assign

let reply = {"_id":"DEADBEEF","_rev":"2-FEEDME","name":"Jimmy Strawson","link":"placeholder.txt","entries":{"Foo":0}};

Object.assign(reply.entries, {
    Bar: 30,
    Baz: 4,
    'Bar Baz': 0
});

console.log('reply =', reply);

edited Oct 13 '16 at 04:34

answered Oct 13 '16 at 04:29

Phil

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@DivyanshuMaithani it's probably the `let`. What browser are you running? – Phil Oct 13 '16 at 04:36
Yeah, must be it. My Chrome is a bit outdated. Maybe using strict mode will do the trick. – Divyanshu Maithani Oct 13 '16 at 04:37
@DivyanshuMaithani no, it won't. `let` is available from Chrome 41.0 which is over a year old now. In any case, this is just an example to run here on StackOverflow – Phil Oct 13 '16 at 04:42

kukkuz · Accepted Answer · 2016-10-13T04:31:53.653

3

reply['entries'].push({"Bar": 0}) does not work as entries is not of type Array but just a plain Object.

Use reply['entries']["Bar"] or reply.entries.Bar. See demo below:

var reply = {
  "_id": "DEADBEEF",
  "_rev": "2-FEEDME",
  "name": "Jimmy Strawson",
  "link": "placeholder.txt",
  "entries": {
    "Foo": 0,
    "Bar": 30,
    "Baz": 4
  }
}
reply['entries']["Bar"] = 0;

console.log(reply);

edited Oct 13 '16 at 04:31

answered Oct 13 '16 at 04:22

kukkuz

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thank you sir! will accept in 8 minutes when it lets me – Hubert S. Cumberdale Oct 13 '16 at 04:23
1

There is no Array [*type*](http://ecma-international.org/ecma-262/7.0/index.html#sec-ecmascript-data-types-and-values). There is a built–in Array constructor from which array instances can be created. The constructor and its instances are type [*Object*](http://ecma-international.org/ecma-262/7.0/index.html#sec-object-type). ;-) – RobG Oct 13 '16 at 04:29
Exactly! An `Array` is a special `Object`- that's what I tried to convey :) – kukkuz Oct 13 '16 at 04:31

Keith Nicholas · Answer 4 · 2016-10-13T04:32:45.563

2

it becomes an object, so just add what you want :-

reply.entries.Foo = 0
reply.entries.Bar = 30
reply.entries.Baz = 4

or reply["entries"]["Foo"] = 0

or reply.entries["Foo"] = 0

edited Oct 13 '16 at 04:32

answered Oct 13 '16 at 04:21

Keith Nicholas

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Your `Object.assign` example will remove the `Foo` property from `reply.entries` – Phil Oct 13 '16 at 04:31
yeah, need the spread operator, but that's not really part of js yet – Keith Nicholas Oct 13 '16 at 04:33
Not really, you just need to operate on `reply.entries` and not `reply` – Phil Oct 13 '16 at 04:36

Divyanshu Maithani · Answer 5 · 2016-10-13T04:25:47.447

1

In order to insert new entries into the JSON object, you could try something like this:

object["someproperty"] = somevalue; or object.someproperty = somevalue;

Say you've got the key and values in variables someproperty and somevalue, you could simply insert them as:

reply.entries[someproperty] = somevalue

edited Oct 13 '16 at 04:25

answered Oct 13 '16 at 04:24

Divyanshu Maithani

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score 1 · Answer 6 · edited Oct 13 '16 at 06:58

1

Here is the alternate method:

reply = {
          "_id": "DEADBEEF",
          "_rev": "2-FEEDME",
          "name": "Jimmy Strawson",
          "link": "placeholder.txt",
          "entries": {
            "Foo": 0
          }
        }
reply.entries.Bar=30;
reply.entries.Baz=4;
reply["entries"]["Bar"]=30;
reply["entries"]["Baz"]=4;

edited Oct 13 '16 at 06:58

Kruti Patel

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answered Oct 13 '16 at 05:37

Jyforzs

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Appending to a JS object that is not an array?

6 Answers6

Note: this will not mutate the original input object, but instead return a new one (typically a good thing).