# Changing global variable inside the function node

**URL:** <https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757>\
**Category:** General\
**Created:** [8 March 2019 22:21 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757 "2019-03-08T22:21:02Z")\
**Posts on this page:** 20\
**Page:** 2

<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:** [10 March 2019 15:52 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/21 "2019-03-10T15:52:52Z")

</div>

Yes, it really is possible with 1 line of code! 😄

All praise the bountiful wisdom of Nick and Dave who made that possible - obviously that isn't standard JavaScript, it is a core function in Node-RED.

The second syntax uses JavaScript's array subscript format. You can use that format instead of the dot notation, while generally discouraged, it is really useful if you end up with an object that contains properties who's names are not valid for the dot notation.

For example:

```
var fred = {"one": 1, "two.jimbob": 2}

```

While you can access the first property with `fred.one`, you cannot do that with the second property since the property name contains a dot. Instead you can use `fred['two.jimbob']`.

This is also useful when you want to use a variable to access a property:

```auto
var whome = 'one'
var fred = {"one": 1, "two.jimbob": 2}

console.log( fred[whome] ) // prints "1"

```

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [10 March 2019 16:17 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/22 "2019-03-10T16:17:52Z")

</div>

So, do you thing it is possible instead of:

```auto
var p = {};
p=msg.payload;
switch (msg.topic) {
case "obed03" : 
    var obed = global.get("obed03"); 
    obed.payload.POWER=p;
    obed.payload.enabled=true;
    global.set("obed03",obed);
    break;
.....

```

I can write:

```auto
switch (msg.topic) {
case "obed03":
    global.set("[msg.topic].payload.POWER", msg.payload);
    global.set("[msg.topic].payload.enabled", true);
    break;
......

```

---

<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:** [10 March 2019 17:27 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/23 "2019-03-10T17:27:19Z")

</div>

Better to do:

```auto
switch (msg.topic) {
case "obed03":
    global.set(msg.topic + ".payload.POWER", msg.payload);
    global.set(msg.topic + ".payload.enabled", true);
    break;
......

```

Or even (assuming you are using Node.JS v8+) - note the backticks instead of double quotes:

```auto
switch (msg.topic) {
case "obed03":
    global.set(`${msg.topic}.payload.POWER`, msg.payload);
    global.set(`${msg.topic}.payload.enabled`, true);
    break;
......

```

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [10 March 2019 17:50 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/24 "2019-03-10T17:50:00Z")

</div>

Thanks. I will check.  
BTW, this is exactly an example what is killing me while I am working with Node.JS/Node-Red.

Soooo many different syntaxes to achieve the same goal. How can I be sure, which syntax is the proper one, which syntax to use. Here I am really missing Python syntax purism and predictability.

Is there some manual of RECENT (Node.JSv8+??) syntax, please?  
Otherwise, I am really LOST.

Thank you anyway

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [10 March 2019 18:31 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/25 "2019-03-10T18:31:25Z")

</div>

One more question to this topic.  
What is the proper code inside the function node?

```auto
var msg3 = {};
a3=global.get("obed03");
msg3.payload=a3.payload.POWER;
msg3.enabled=a3.payload.enabled;
return msg3;

```

or directly:

```auto
var msg3 = {};
msg3.payload=global.get("obed03.payload.POWER");
msg3.enabled=global.get("obed03.payload.template");
return msg3;

```

---

<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:** [10 March 2019 21:04 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/26 "2019-03-10T21:04:33Z")

</div>

> [@Petr](#):
>
> Here I am really missing Python syntax purism and predictability.

Hmm, v2 vs v3? It is true that JS can have a few too many ways to do the same things - but each language has its own quirks.

> [@Petr](#):
>
> manual of RECENT (Node.JSv8+??) syntax

For Node.js itself, simply check the Node.js website - it has an excellent manual. For JavaScript in general, the Mozilla Developer Network (MDN) is generally the best and most accurate source.

However, I always have to do a LOT of Googling (actually I mainly use DuckDuckGo these days to avoid tracking) since I'm not a full-time pro developer.

Then use a good IDE such as VScode where you can create your own snippets. VScode is actually built using Node.js and Electron and its native understanding of Node and npm packages is outstanding. Also install and configure JSlint for VScode as this will catch all of the little annoying errors before you get as far as running your code.

For function nodes, the built-in ACE editor is pretty good too. It will catch a load of issues for you so pay attention to the error and warning icons it gives you. Use the library feature to remember snippets of code for things that you struggle to remember. For example, I always struggle to remember the right syntax for JavaScript select/case statements. So saving a template one to the library means I can simply reproduce a sample when I need to.

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [10 March 2019 23:03 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/27 "2019-03-10T23:03:01Z")

</div>

Thank you for sharing your experience and for your suggestions.  
Anyway, your help is really GREAT.!!!!!  
My NR `SELECT / CASE` statement in my function node was 78 lines of code.  
Now, thanks to your help, no more SELECT / CASE statement and 3 lines of code only!!! 😃

```auto
[{"id":"509784e2.ebf6fc","type":"function","z":"f2e2f228.998238","name":"CASE set recent ENERGY values to globals (obedXX)","func":"var total = msg.payload.Total;\nvar today = msg.payload.Today;\nvar yesterday = msg.payload.Yesterday;\n\nswitch (msg.topic) {\ncase \"obed03\" : \n var obed = global.get(\"obed03\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed03\",obed);\n break;\ncase \"obed04\" : \n var obed = global.get(\"obed04\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed04\",obed);\n break;\ncase \"obed05\" : \n var obed = global.get(\"obed05\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed05\",obed);\n break;\ncase \"obed06\" : \n var obed = global.get(\"obed06\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed06\",obed);\n break;\ncase \"obed07\" :\n var obed = global.get(\"obed07\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed07\",obed);\n break;\ncase \"obed08\" : \n var obed = global.get(\"obed08\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed08\",obed);\n break;\ncase \"obed09\" : \n var obed = global.get(\"obed09\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed09\",obed);\n break;\ncase \"obed10\" : \n var obed = global.get(\"obed10\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed10\",obed);\n break;\ncase \"obed11\" : \n var obed = global.get(\"obed11\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed11\",obed);\n break;\ncase \"obed12\" : \n var obed = global.get(\"obed12\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed12\",obed);\n break;\n}\n\nreturn msg;","outputs":1,"noerr":0,"x":1720,"y":1140,"wires":[[]]},{"id":"1e597e7a.9bd5ca","type":"function","z":"f2e2f228.998238","name":"NEW dynamic set recent ENERGY values to globals (obedXX)","func":"global.set(msg.topic + \".payload.Total\", msg.payload.Total);\nglobal.set(msg.topic + \".payload.Today\", msg.payload.Today);\nglobal.set(msg.topic + \".payload.Yesterday\", msg.payload.Yesterday);\n","outputs":1,"noerr":0,"x":1740,"y":1200,"wires":[[]]}]

```

I wonder, why it is not possible within a `change node`. Something like:  
 ![Screenshot%20from%202019-03-11%2000-02-23](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/a/a83a805d7c51fc898fdf056d4c5f262e31f61042.png)

---

<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:** [11 March 2019 01:26 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/28 "2019-03-11T01:26:36Z")

</div>

You can probably do it with JSONata as it can also access global vars. I don't think that the global var setting is designed to work with variables but JSONata certainly is.

---

<div class="post-metadata">

**Author:** ![Andrei](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrei/32/10446_2.png) [@Andrei](https://discourse.nodered.org/u/Andrei)\
**Post date:** [11 March 2019 06:32 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/29 "2019-03-11T06:32:33Z")

</div>

Very interesting thread indeed.

I could not understand why the final solution needs 3 global.set lines in the function node. Can´t it be reduced to one line of the kind?

```auto
global.set(msg.topic); // for testing only. Clear the the global property.

//global.set(msg.topic + ".payload.Total", msg.payload.Total);
//global.set(msg.topic + ".payload.Today", msg.payload.Today);
//global.set(msg.topic + ".payload.Yesterday", msg.payload.Yesterday);

global.set(msg.topic, {"payload" : msg.payload});
return msg;

```

It would not be a matter of optimization but making the code easier to understand. Using three lines seems to introduce unnecessary redundancy to the code.

Testing flow:

```auto
[{"id":"f05ed819.d29b38","type":"tab","label":"Flow 3","disabled":false,"info":""},{"id":"4089bbcc.d1db34","type":"function","z":"f05ed819.d29b38","name":"NEW ","func":"global.set(msg.topic); // for testing only. Clear the the global property.\n\n//global.set(msg.topic + \".payload.Total\", msg.payload.Total);\n//global.set(msg.topic + \".payload.Today\", msg.payload.Today);\n//global.set(msg.topic + \".payload.Yesterday\", msg.payload.Yesterday);\n\nglobal.set(msg.topic, {\"payload\" : msg.payload});\nreturn msg;\n","outputs":1,"noerr":0,"x":510,"y":100,"wires":[["ade2fd71.cf45e"]]},{"id":"5f409428.4e3f1c","type":"change","z":"f05ed819.d29b38","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"obed1","tot":"str"},{"t":"set","p":"payload.Total","pt":"msg","to":"3","tot":"num"},{"t":"set","p":"payload.Today","pt":"msg","to":"2","tot":"num"},{"t":"set","p":"payload.Yesterday","pt":"msg","to":"1","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":340,"y":100,"wires":[["4089bbcc.d1db34"]]},{"id":"8a723c98.cda02","type":"inject","z":"f05ed819.d29b38","name":"","topic":"","payload":"{}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":100,"wires":[["5f409428.4e3f1c"]]},{"id":"ade2fd71.cf45e","type":"debug","z":"f05ed819.d29b38","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":630,"y":100,"wires":[]},{"id":"9b27cc43.fce5d","type":"function","z":"f05ed819.d29b38","name":"NEW ","func":"global.set(msg.topic); // for testing only. Clear the the global property.\n\nglobal.set(msg.topic + \".payload.Total\", msg.payload.Total);\nglobal.set(msg.topic + \".payload.Today\", msg.payload.Today);\nglobal.set(msg.topic + \".payload.Yesterday\", msg.payload.Yesterday);\n\n//global.set(msg.topic, msg.payload);\nreturn msg;\n","outputs":1,"noerr":0,"x":510,"y":160,"wires":[["194a52c3.21f5dd"]]},{"id":"e4be4713.86f5d8","type":"change","z":"f05ed819.d29b38","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"obed1","tot":"str"},{"t":"set","p":"payload.Total","pt":"msg","to":"3","tot":"num"},{"t":"set","p":"payload.Today","pt":"msg","to":"2","tot":"num"},{"t":"set","p":"payload.Yesterday","pt":"msg","to":"1","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":340,"y":160,"wires":[["9b27cc43.fce5d"]]},{"id":"9ce989c7.439138","type":"inject","z":"f05ed819.d29b38","name":"","topic":"","payload":"{}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":160,"wires":[["e4be4713.86f5d8"]]},{"id":"194a52c3.21f5dd","type":"debug","z":"f05ed819.d29b38","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":630,"y":160,"wires":[]}]

```

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [11 March 2019 14:33 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/30 "2019-03-11T14:33:35Z")

</div>

Hmmm. This was exactly the reason for my long nights sitting in front of the screen pulling my hair out 😃  
I didn’t understand, the code you are suggesting,

```auto
global.set(msg.topic, {"payload" : msg.payload});

```

is overwriting (re-instantiating) a global variable COMPLETELY. It is not changing property values as I intended.  
It means ALL other values stored in the global variable properties are LOST. See the example below:

```auto
[{"id":"cd8f21e1.31158","type":"function","z":"5085dcc5.5bf8dc","name":"set globals (obedXX)","func":"// rybarska mista bez chaticek\nvar r1='<left> <font size=\"4\">';\nvar r2='<img src=\"/verejne/icons/misc/man-fishing.png\" height=\"42\" width=\"42\"> </font></left>';\n\n// rybarska mista s chatickou\nvar c1='<left> <font size=\"4\">';\nvar c2='<img src=\"/verejne/icons/misc/NicePng_house-icon-png_147010.png\" height=\"36\" width=\"36\"> </font></left>';\n\n// rybarska mista bez chaticek\nglobal.set(\"obed03\",{payload:{template:r1+3+r2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed04\",{payload:{template:r1+4+r2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed05\",{payload:{template:r1+5+r2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed10\",{payload:{template:r1+1+r2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed11\",{payload:{template:r1+11+r2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\n\n// rybarska mista s chatickou\nglobal.set(\"obed06\",{payload:{template:c1+6+c2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed07\",{payload:{template:c1+7+c2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed08\",{payload:{template:c1+8+c2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed09\",{payload:{template:c1+9+c2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nglobal.set(\"obed12\",{payload:{template:c1+12+c2, Total:0, Today:0, Yesterday:0, POWER:0, enabled:false}});\nnode.warn(global.get(\"obed03\"));\nreturn msg;","outputs":1,"noerr":0,"x":340,"y":260,"wires":[["34a238ea.41b6b","c0b37f64.08f49","ff0c7997.cf8a7"]]},{"id":"5fa35193.735a4","type":"function","z":"5085dcc5.5bf8dc","name":"new dynamic","func":"\nglobal.set(msg.topic + \".payload.Total\", msg.payload.Total);\nglobal.set(msg.topic + \".payload.Today\", msg.payload.Today);\nglobal.set(msg.topic + \".payload.Yesterday\", msg.payload.Yesterday);\nnode.warn(global.get(msg.topic));\n\n\n","outputs":1,"noerr":0,"x":810,"y":300,"wires":[[]]},{"id":"b7327526.7024e8","type":"inject","z":"5085dcc5.5bf8dc","name":"","topic":"","payload":"{}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":260,"wires":[["cd8f21e1.31158"]]},{"id":"34a238ea.41b6b","type":"change","z":"5085dcc5.5bf8dc","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"obed04","tot":"str"},{"t":"set","p":"payload.Total","pt":"msg","to":"3","tot":"num"},{"t":"set","p":"payload.Today","pt":"msg","to":"2","tot":"num"},{"t":"set","p":"payload.Yesterday","pt":"msg","to":"1","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":600,"y":300,"wires":[["5fa35193.735a4"]]},{"id":"c0b37f64.08f49","type":"change","z":"5085dcc5.5bf8dc","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"obed03","tot":"str"},{"t":"set","p":"payload.Total","pt":"msg","to":"400","tot":"num"},{"t":"set","p":"payload.Today","pt":"msg","to":"400","tot":"num"},{"t":"set","p":"payload.Yesterday","pt":"msg","to":"400","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":600,"y":240,"wires":[["c6b857e2.37efa"]]},{"id":"c6b857e2.37efa","type":"function","z":"5085dcc5.5bf8dc","name":"old static original","func":"var total =300;\nvar today = 300;\nvar yesterday = 300;\nvar obed = global.get(\"obed03\"); \n obed.payload.Total=total;\n obed.payload.Today=today;\n obed.payload.Yesterday=yesterday;\n global.set(\"obed03\",obed);\nnode.warn(global.get(\"obed03\"));\n\n","outputs":1,"noerr":0,"x":820,"y":240,"wires":[[]]},{"id":"40719069.a4e8e","type":"function","z":"5085dcc5.5bf8dc","name":"Andrei","func":"global.set(msg.topic); // for testing only. Clear the the global property.\n\n//global.set(msg.topic + \".payload.Total\", msg.payload.Total);\n//global.set(msg.topic + \".payload.Today\", msg.payload.Today);\n//global.set(msg.topic + \".payload.Yesterday\", msg.payload.Yesterday);\n\nglobal.set(msg.topic, {\"payload\" : msg.payload});\n\nnode.warn(global.get(msg.topic));\nreturn msg;\n","outputs":1,"noerr":0,"x":790,"y":380,"wires":[[]]},{"id":"ff0c7997.cf8a7","type":"change","z":"5085dcc5.5bf8dc","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"obed05","tot":"str"},{"t":"set","p":"payload.Total","pt":"msg","to":"500","tot":"num"},{"t":"set","p":"payload.Today","pt":"msg","to":"500","tot":"num"},{"t":"set","p":"payload.Yesterday","pt":"msg","to":"500","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":600,"y":380,"wires":[["40719069.a4e8e"]]}]

```

---

<div class="post-metadata">

**Author:** ![Andrei](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrei/32/10446_2.png) [@Andrei](https://discourse.nodered.org/u/Andrei)\
**Post date:** [11 March 2019 15:19 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/31 "2019-03-11T15:19:24Z")

</div>

Hi Petr, I (wrongly) assumed that there were no other properties in msg.payload so the code snippet I proposed will not work indeed. Your last flow clearly (and brilliantly) demonstrated that. I take the opportunity to thank you for opening this thread as I could learn something new about the global context.

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [11 March 2019 15:59 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/32 "2019-03-11T15:59:30Z")

</div>

Thank you Andrei.  
Anyway, I feel I am lost in this new word of JavaScritp, mainly because of so many different syntax flavours ...  
Indeed, the whole NR IDE looks to me kind of unfriendly for debugging purposes...  
But I am trying to continue 😃  
I will try the environment Julian Knight is using (see his post above).

---

<div class="post-metadata">

**Author:** ![Andrei](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrei/32/10446_2.png) [@Andrei](https://discourse.nodered.org/u/Andrei)\
**Post date:** [13 March 2019 06:57 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/33 "2019-03-13T06:57:21Z")

</div>

Hi Petr,

Indeed it is possible to the functions `flowContext` and `globalContext`in a JSONata expression to get values from flow and global context. As far as I remember it is not possible to set values to the context via JSONata.

If you want to play with JSONata it is worth to [read this enlightening thread.](https://discourse.nodered.org/t/access-to-context-stores-in-jsonata-expressions/8738/8)

I don't think it is possible to use a JSONata expression in the change node in the way you illustrated above.

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [13 March 2019 10:02 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/34 "2019-03-13T10:02:41Z")

</div>

Andrei, thanks for your interest.  
I was looking already for JSONata solution/approach.  
It looks to me far complicated, comparing to a `function node` easy approach. Because of that, I think not worth to investigate it deeper...

---

<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:** [13 March 2019 10:29 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/35 "2019-03-13T10:29:54Z")

</div>

As a founder member of NUAGV [1] I have to point out that all this stress over setting variables can be avoided by not using global (or flow) context to store variables. Instead use messages to pass data to the places it is needed, which is what node-red is all about. There may possibly be a few occasions in which it is better to use context (for variable data) but I have so far not needed to use it.

[1] Node red Users Against Global (and flow) Variables. Any offers of a more snappy acronym gratefully received.

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [13 March 2019 10:44 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/36 "2019-03-13T10:44:25Z")

</div>

I see. Thank you for your advise, I am using the NR few weeks only, so this is all new to me.  
I will investigate. Can you, please, give some point to resources where to get info and examples how to use `NR messages`?

---

<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:** [13 March 2019 11:23 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/37 "2019-03-13T11:23:02Z")

</div>

The whole node red system is based on messages. That is what `msg` is referring to when you use `msg.payload` etc. When you join nodes up you are providing the wires along which the messages flow.

---

<div class="post-metadata">

**Author:** ![ukmoose](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ukmoose/32/13_2.png) [@ukmoose](https://discourse.nodered.org/u/ukmoose)\
**Post date:** [13 March 2019 11:31 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/38 "2019-03-13T11:31:54Z")

</div>

There’s the getting started part on the website [https://nodered.org/docs/getting-started/first-flow](https://nodered.org/docs/getting-started/first-flow)

and several Node-RED tutorials online which you can find using google

---

<div class="post-metadata">

**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [13 March 2019 12:12 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/39 "2019-03-13T12:12:08Z")

</div>

I was not reading properly your post, sorry. I was thinking there is some mysterious message variable or so on, which I do not see. Sorry about my confusing reply.  
I am in the situation, where I do need to keep the state of Sonoff/Tasmota switch (on/off, available/not available) and compare it with the incoming mqtt information. For this purposes, I am using global variables. Is this approach wrong? I can not imaging how to do it the other way, because flows are not connected.

---

<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:** [13 March 2019 12:20 UTC](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757/40 "2019-03-13T12:20:29Z")

</div>

Is not that state already available in mqtt from the Sonoff. Why do you need to store it locally too?

[Previous page](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757.md?page=1)

[Next page](https://discourse.nodered.org/t/changing-global-variable-inside-the-function-node/8757.md?page=3)