# Function - Insert additional keys from matching keys in array of objects

**URL:** <https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962>\
**Category:** General\
**Created:** [26 March 2023 14:54 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962 "2023-03-26T14:54:05Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![mgottholsen](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/mgottholsen/32/61686_2.png) [@mgottholsen](https://discourse.nodered.org/u/mgottholsen)\
**Post date:** [26 March 2023 14:54 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962/1 "2023-03-26T14:54:05Z")

</div>

Hey all, I'm struggling with JS & looping through an array of objects, matching a key in each object and inserting associated values into another separate object.

I have this array of objects:

```auto
const cameraData = [
    { entity_name:"camera.1", lat: 31.2345, lon: -81.2345 },
    { entity_name:"camera.2", lat: 32.2345, lon: -81.2345 },
    { entity_name:"camera.3", lat: 33.2345, lon: -81.2345 },
    { entity_name:"camera.4", lat: 34.2345, lon: -81.2345 },
    { entity_name:"camera.5", lat: 35.2345, lon: -81.2345 },
    { entity_name:"camera.6", lat: 36.2345, lon: -81.2345 }
 ];

```

and I'm trying to match the first key "entity\_name" to an incoming msg.payload single object from another function that emits a series of objects as they are queried earlier in the flow. The object looks like this:

```auto
{
  "attributes": 0,
  "context": 0,
  "last_changed": "2023-03-26T13:04:26.517Z",
  "last_updated": "2023-03-26T14:44:23.734Z",
  "timeSinceChangedMs": 6252438,
  "name": "Camera 1 - Front",
  "entity_name": "camera.1",
  "photoUrl": "http://0.0.0.0:8123/api/camera_proxy/camera.garden_shed_high?token=abc123"
}

```

I would like to append the keys "lat" and "lon" to each matching object, so it would look like this:

```auto
{
  "attributes": 0,
  "context": 0,
  "last_changed": "2023-03-26T13:04:26.517Z",
  "last_updated": "2023-03-26T14:44:23.734Z",
  "timeSinceChangedMs": 6252438,
  "name": "Camera 1 - Front",
  "entity_name": "camera.1",
  "photoUrl": "http://0.0.0.0:8123/api/camera_proxy/camera.garden_shed_high?token=abc123"
  "lat": "31.2345",
  "lon": "-81.2345"
}

```

Can anyone assist me please? Thanks!

---

<div class="post-metadata">

**Author:** ![marcus-j-davies](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/marcus-j-davies/32/103435_2.png) [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)\
**Post date:** [26 March 2023 15:03 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962/2 "2023-03-26T15:03:05Z")

</div>

Hi @mgottholsen

If I understand your requirement:

You can use the `find` method for an array, and use the found array item, to extract the values you need, and then add them to the incoming `payload`.

```js
const cameraData = [
    { entity_name:"camera.1", lat: 31.2345, lon: -81.2345 },
    { entity_name:"camera.2", lat: 32.2345, lon: -81.2345 },
    { entity_name:"camera.3", lat: 33.2345, lon: -81.2345 },
    { entity_name:"camera.4", lat: 34.2345, lon: -81.2345 },
    { entity_name:"camera.5", lat: 35.2345, lon: -81.2345 },
    { entity_name:"camera.6", lat: 36.2345, lon: -81.2345 }
 ]

const matchedCamera = cameraData.find((Camera) => Camera.entity_name === msg.payload.entity_name)

if(matchedCamera !== undefined){
  msg.payload.lat = matchedCamera.lat
  msg.payload.lon = matchedCamera.lon
}

return msg;

```

---

<div class="post-metadata">

**Author:** ![mgottholsen](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/mgottholsen/32/61686_2.png) [@mgottholsen](https://discourse.nodered.org/u/mgottholsen)\
**Post date:** [26 March 2023 15:15 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962/3 "2023-03-26T15:15:30Z")

</div>

That was exactly it, thank you! Definitely more simple than what I was trying to do.

---

<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [26 March 2023 16:28 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962/4 "2023-03-26T16:28:20Z")

</div>

> [@mgottholsen](#):
>
> Hey all, I'm struggling with JS & looping through an array of objects, matching a key in each object and inserting associated values into another separate object.
> 
> I have this array of objects:
> 
> ```auto
> const cameraData = [
> { entity_name:"camera.1", lat: 31.2345, lon: -81.2345 },
> { entity_name:"camera.2", lat: 32.2345, lon: -81.2345 },
> { entity_name:"camera.3", lat: 33.2345, lon: -81.2345 },
> { entity_name:"camera.4", lat: 34.2345, lon: -81.2345 },
> { entity_name:"camera.5", lat: 35.2345, lon: -81.2345 },
> { entity_name:"camera.6", lat: 36.2345, lon: -81.2345 }
> ];
> 
> ```

If that is your own array, I would structure it as a lookup object.  
e.g.

```auto
{
    "camera.1":{"lat":31.2345,"lon":-81.2345},
    "camera.2":{"lat":32.2345,"lon":-81.2345},
    "camera.3":{"lat":33.2345,"lon":-81.2345},
    "camera.4":{"lat":34.2345,"lon":-81.2345},
    "camera.5":{"lat":35.2345,"lon":-81.2345},
    "camera.6":{"lat":36.2345,"lon":-81.2345}
}

```

That way you could do a simple lookup. You can add a if(msg.payload.lat) to return or not also.

```auto
const lookup = {
    "camera.1":{"lat":31.2345,"lon":-81.2345},
    "camera.2":{"lat":32.2345,"lon":-81.2345},
    "camera.3":{"lat":33.2345,"lon":-81.2345},
    "camera.4":{"lat":34.2345,"lon":-81.2345},
    "camera.5":{"lat":35.2345,"lon":-81.2345},
    "camera.6":{"lat":36.2345,"lon":-81.2345}
}

Object.assign(msg.payload, lookup[msg.payload.entity_name])
return msg;

```

Or You could also do it in a change node  
e.g.

```auto
[{"id":"68cb0bbef3e3b379","type":"inject","z":"65617ffeb779f51c","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"{ \"attributes\": 0, \"context\": 0, \"last_changed\": \"2023-03-26T13:04:26.517Z\", \"last_updated\": \"2023-03-26T14:44:23.734Z\", \"timeSinceChangedMs\": 6252438, \"name\": \"Camera 1 - Front\", \"entity_name\": \"camera.1\", \"photoUrl\": \"http://0.0.0.0:8123/api/camera_proxy/camera.garden_shed_high?token=abc123\" }","payloadType":"json","x":130,"y":4180,"wires":[["f1d77eb605782d62","bc9516c595e48c9d"]]},{"id":"f1d77eb605782d62","type":"function","z":"65617ffeb779f51c","name":"function 21","func":"const lookup = {\n \"camera.1\":{\"lat\":31.2345,\"lon\":-81.2345},\n \"camera.2\":{\"lat\":32.2345,\"lon\":-81.2345},\n \"camera.3\":{\"lat\":33.2345,\"lon\":-81.2345},\n \"camera.4\":{\"lat\":34.2345,\"lon\":-81.2345},\n \"camera.5\":{\"lat\":35.2345,\"lon\":-81.2345},\n \"camera.6\":{\"lat\":36.2345,\"lon\":-81.2345}\n}\n\nObject.assign(msg.payload, lookup[msg.payload.entity_name])\nif(msg.payload.lat) return msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":310,"y":4180,"wires":[["165ab9717d3ff499"]]},{"id":"bc9516c595e48c9d","type":"change","z":"65617ffeb779f51c","name":"","rules":[{"t":"set","p":"lookup","pt":"msg","to":"{\"camera.1\":{\"lat\":31.2345,\"lon\":-81.2345},\"camera.2\":{\"lat\":32.2345,\"lon\":-81.2345},\"camera.3\":{\"lat\":33.2345,\"lon\":-81.2345},\"camera.4\":{\"lat\":34.2345,\"lon\":-81.2345},\"camera.5\":{\"lat\":35.2345,\"lon\":-81.2345},\"camera.6\":{\"lat\":36.2345,\"lon\":-81.2345}}","tot":"json"},{"t":"set","p":"payload.lat","pt":"msg","to":"lookup[msg.payload.entity_name].lat","tot":"msg"},{"t":"set","p":"payload.lon","pt":"msg","to":"lookup[msg.payload.entity_name].lon","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":320,"y":4240,"wires":[["d778b812bb579cea"]]},{"id":"165ab9717d3ff499","type":"debug","z":"65617ffeb779f51c","name":"debug 253","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":490,"y":4180,"wires":[]},{"id":"d778b812bb579cea","type":"debug","z":"65617ffeb779f51c","name":"debug 252","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":510,"y":4240,"wires":[]}]

```

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---

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [9 April 2023 16:29 UTC](https://discourse.nodered.org/t/function-insert-additional-keys-from-matching-keys-in-array-of-objects/76962/5 "2023-04-09T16:29:12Z")

</div>

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