# Json Data Mapping

**URL:** <https://discourse.nodered.org/t/json-data-mapping/66914>\
**Category:** General\
**Created:** [25 August 2022 15:10 UTC](https://discourse.nodered.org/t/json-data-mapping/66914 "2022-08-25T15:10:37Z")\
**Posts on this page:** 14\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ryanshafer](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryanshafer/32/59128_2.png) [@Ryanshafer](https://discourse.nodered.org/u/Ryanshafer)\
**Post date:** [25 August 2022 15:10 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/1 "2022-08-25T15:10:37Z")

</div>

Hi,

I currently have a function node that maps [this nasa data](https://ssd-api.jpl.nasa.gov/cad.api?date-min=now&dist-max=0.2) to an object for use later in the flow. I'm not totally happy with it because it occasionally throws an error. I could add some better error handling, but I was wondering if there was a more node-red way than a function node to convert this JSON data into an object, like so:

```auto
{
   "des":"2022 OU1",
   "orbit_id":"6",
   "jd":"2459817.400619856",
   "cd":"2022-Aug-25 21:37",
   "dist":"0.138855530107527",
   "dist_KM":"20772520",
   "dist_min":"0.13885499498311",
   "dist_max":"0.13885606523237",
   "v_rel":"7.62854662977278",
   "speed":"8km/s",
   "v_inf":"7.62603081310743",
   "t_sigma_f":"< 00:01",
   "h":"22.03",
   "size_min":"104",
   "size_max":"233"
}

```

Thanks for any help!

---

<div class="post-metadata">

**Author:** ![ScheepersJohan](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/scheepersjohan/32/39556_2.png) [@ScheepersJohan](https://discourse.nodered.org/u/ScheepersJohan)\
**Post date:** [25 August 2022 15:25 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/2 "2022-08-25T15:25:38Z")

</div>

Try change node.

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [25 August 2022 15:41 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/3 "2022-08-25T15:41:09Z")

</div>

Realistically, there are two methods to transform one JSON structure into another:

1. Use a change node with JSONata
2. Use a function node.

Occasionally, you might find a (2.a) which would be to use a node.js module with a function node if you can find a module that does the bulk of the processing you want.

JSONata is great if you can work out the transform. I generally recommend giving it 10 minutes, if you haven't worked it out by then, you should go back to a function.

Oddly enough, a function node is often less processing overhead anyway.

Sometimes though, you get lucky and one of the JSONata guru's takes an interest and posts an answer 🙂

Other times, not so much.

---

<div class="post-metadata">

**Author:** ![hardillb](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/hardillb/32/12373_2.png) [@hardillb](https://discourse.nodered.org/u/hardillb)\
**Post date:** [25 August 2022 15:46 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/4 "2022-08-25T15:46:49Z")

</div>

It would probably help if you showed us what the error is

---

<div class="post-metadata">

**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [25 August 2022 15:48 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/5 "2022-08-25T15:48:43Z")

</div>

Did you start by sending it through a JSON node to convert it to a JavaScript object?

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<div class="post-metadata">

**Author:** ![Ryanshafer](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryanshafer/32/59128_2.png) [@Ryanshafer](https://discourse.nodered.org/u/Ryanshafer)\
**Post date:** [25 August 2022 16:00 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/6 "2022-08-25T16:00:46Z")

</div>

Thanks, I can sort that out myself, I'm not looking for help with the function node. I'm looking to see if there is a more node-red way of doing it.

---

<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:** [25 August 2022 16:01 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/7 "2022-08-25T16:01:14Z")

</div>

Why? The http request node can be set to output a json object.

@Ryanshafer You don't say if you parse all the arrays or if you after a specific one.  
here is an example of using Javascript and JSONata to map all the values to an array of objects.

```auto
[{"id":"88aeec8c.8e386","type":"inject","z":"9a86d59e88442f2c","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"<?xml version=\"1.0\" encoding=\"utf-8\" ?> <!DOCTYPE data [<!ELEMENT data (parameter+)> <!ELEMENT parameter (name,value)> <!ELEMENT name (#PCDATA)> <!ELEMENT value (#PCDATA)>]> <data> <parameter> \t<name>DB_L2174_ALARMS</name> \t<value><![CDATA[0000000000000111000000000000000]]></value> </parameter> <parameter> \t<name>DB_DEMOD_LICENCE_OPTIONS</name> \t<value><![CDATA[1110010000000000000001000000000000000000]]></value> </parameter> <parameter> \t<name>DB_DECOD_LICENCE_OPTIONS</name> \t<value><![CDATA[0000000000000000000000000000000000000000]]></value> </parameter> <parameter> \t<name>DB_DEMOD_SELFTEST_RESULTS</name> \t<value><![CDATA[100000000000000000000000000000000]]></value> </parameter> <parameter> \t<name>DB_L2174_RX_MODE</name> \t<value><![CDATA[DVBT]]></value> </parameter> <parameter> \t<name>DB_L2174_FREQ1</name> \t<value><![CDATA[2.030000]]></value> </parameter> </data>","payloadType":"str","x":70,"y":300,"wires":[["e129cb3.1181238"]]},{"id":"e129cb3.1181238","type":"http request","z":"9a86d59e88442f2c","name":"","method":"GET","ret":"obj","paytoqs":"ignore","url":"https://ssd-api.jpl.nasa.gov/cad.api?date-min=now&dist-max=0.2","tls":"","persist":false,"proxy":"","authType":"","x":240,"y":300,"wires":[["72662c0b.42bec4","df71d57e.fe9248"]]},{"id":"72662c0b.42bec4","type":"change","z":"9a86d59e88442f2c","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$$.payload.data@$a.($$.payload.fields#$i.${$: $a[$i]})","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":420,"y":400,"wires":[["995d7e86.aea2f"]]},{"id":"df71d57e.fe9248","type":"function","z":"9a86d59e88442f2c","name":"","func":"msg.payload = msg.payload.data.map(arr => {\n let obj = {};\n msg.payload.fields.forEach((key, index) => {\n obj[key] = arr[index];\n })\n return obj;\n})\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":450,"y":280,"wires":[["9e47108c.90d0f8"]]},{"id":"995d7e86.aea2f","type":"debug","z":"9a86d59e88442f2c","name":"jsonata","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":650,"y":400,"wires":[]},{"id":"9e47108c.90d0f8","type":"debug","z":"9a86d59e88442f2c","name":"javascript","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":630,"y":280,"wires":[]}]

```

Javascript

```auto
msg.payload = msg.payload.data.map(arr => {
    let obj = {};
    msg.payload.fields.forEach((key, index) => {
        obj[key] = arr[index];
    })
    return obj;
})
return msg;

```

JSONata

```auto
$$.payload.data@$a.($$.payload.fields#$i.${$: $a[$i]})

```

---

<div class="post-metadata">

**Author:** ![Ryanshafer](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryanshafer/32/59128_2.png) [@Ryanshafer](https://discourse.nodered.org/u/Ryanshafer)\
**Post date:** [25 August 2022 16:05 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/8 "2022-08-25T16:05:05Z")

</div>

Yea, but the response from the API is designed to save space, so you get a JSON response with all the fields list once and then all the data as separate items without key/value pairs. So I have to construct the final object.

```auto
{
   "signature":{
      "source":"NASA/JPL SBDB Close Approach Data API",
      "version":"1.4"
   },
   "count":"181",
   "fields":[
      "des",
      "orbit_id",
      "jd",
      "cd",
      "dist",
      "dist_min",
      "dist_max",
      "v_rel",
      "v_inf",
      "t_sigma_f",
      "h"
   ],
   "data":[
      [
         "2022 OU1",
         "6",
         "2459817.400619856",
         "2022-Aug-25 21:37",
         "0.138855530107527",
         "0.13885499498311",
         "0.13885606523237",
         "7.62854662977278",
         "7.62603081310743",
         "< 00:01",
         "22.03"
      ]

```

---

<div class="post-metadata">

**Author:** ![Ryanshafer](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryanshafer/32/59128_2.png) [@Ryanshafer](https://discourse.nodered.org/u/Ryanshafer)\
**Post date:** [25 August 2022 16:06 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/9 "2022-08-25T16:06:44Z")

</div>

Thanks, I'll take a look. But can the change node+JSONata iterate over hundreds of items to make one object? I haven't ever used it that way.

---

<div class="post-metadata">

**Author:** ![Ryanshafer](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryanshafer/32/59128_2.png) [@Ryanshafer](https://discourse.nodered.org/u/Ryanshafer)\
**Post date:** [25 August 2022 16:08 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/10 "2022-08-25T16:08:57Z")

</div>

I'm after all of them. Thanks I'll take a look!

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [25 August 2022 16:09 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/11 "2022-08-25T16:09:22Z")

</div>

Yes, it can. If you have a PhD in 10 dimensional quantum physics! 🙂

In other words, it is capable of it but working it out is likely to give you a splitting headache and a desire to retreat to a darkened room.

Doing it with JS is simple and almost certainly faster to write, faster to run and much easier to grok in 6 months time should you need to change it.

---

<div class="post-metadata">

**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [25 August 2022 16:17 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/12 "2022-08-25T16:17:53Z")

</div>

> [@E1cid](#):
>
> Why? The http request node can be set to output a json object.

Even better. I asked because the data was shown as JSON not a JavaScript object, it was not clear that the OP knew that he should start by converting it.

---

<div class="post-metadata">

**Author:** ![hardillb](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/hardillb/32/12373_2.png) [@hardillb](https://discourse.nodered.org/u/hardillb)\
**Post date:** [25 August 2022 20:23 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/13 "2022-08-25T20:23:47Z")

</div>

Yes, but knowing what the error is may be a result of variations in the data that would have an impact on what other approaches to take.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [24 October 2022 20:23 UTC](https://discourse.nodered.org/t/json-data-mapping/66914/14 "2022-10-24T20:23:53Z")

</div>

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