# Using a global variable in the data/json
**URL:** https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145
**Category:** General
**Tags:** home-assistant
**Created:** [20 September 2024 15:26 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145 "2024-09-20T15:26:05Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Crabsticks](https://discourse.nodered.org/u/Crabsticks)
#### Post date: [20 September 2024 15:26 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/1 "2024-09-20T15:26:05Z")
Hello,
I'm trying to create a flow to change the brightness of my light, I can set the brightness directly however I can't figure out how to use a global variable I've set elsewhere in the flow. I'm sure I'm just not using the right syntax.
currently my json looks like this
```auto
{
"entity_id": "light.living_room_main_light_light",
"brightness": 22
}
```
instead of the number 22 I want to use a variable global.brightness put I dom not know how to import the variable into the json correctly.
Thanks in advince
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [20 September 2024 15:33 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/2 "2024-09-20T15:33:03Z")
There are several ways.
The easiest is to pass the `msg` through a change node and set `msg.payload.brightness` to `global.brightness`
> [@Crabsticks](#):
>
> instead of the number 22 I want to use a variable global.brightness put I dom not know how to import the variable into the json correctly.
Assuming you mean a JS Object (JSON is a string), then the above will work.
---
### Author:  [@Crabsticks](https://discourse.nodered.org/u/Crabsticks)
#### Post date: [20 September 2024 15:50 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/3 "2024-09-20T15:50:12Z")
Sorry if JSON is not the correct term.
I'm using a service call node and editing the data field.
I need to be able to pull in the global variable.
I've created a payload message as you suggested, how do I use the payload instead of the 22 value?
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [20 September 2024 15:53 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/4 "2024-09-20T15:53:44Z")
> [@Crabsticks](#):
>
> I'm using a service call node
I have no idea what that is.
does the nodes field support JSONata? You could use JSONata to grab context values. Or perhaps there is a `msg` fired into this " service call node" in which case you can use the switch node BEFORE it to grab the global value and add it to the payload?
If this is a home assistant node, then please tag the post with #home-assistant so that others are not tripped up too.
---
### Author:  [@Crabsticks](https://discourse.nodered.org/u/Crabsticks)
#### Post date: [20 September 2024 15:59 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/5 "2024-09-20T15:59:14Z")
It is a home assistant node, sorry for the confusion.
I'll try and figure out how to tag the post
---
### Author:  [@E1cid](https://discourse.nodered.org/u/E1cid)
#### Post date: [20 September 2024 16:17 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/6 "2024-09-20T16:17:10Z")
Select J: (jsonata expression) rather than JSON type input.
Then
```auto
{
"entity_id": "light.living_room_main_light_light",
"brightness": globalContext("brightness")
}
```
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [20 September 2024 16:19 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/7 "2024-09-20T16:19:51Z")
> [@Crabsticks](#):
>
> how do I use the payload instead of the 22 value?
```auto
{
"entity_id": "light.living_room_main_light_light",
"brightness": msg.payload
}
```
---
### Author:  [@Crabsticks](https://discourse.nodered.org/u/Crabsticks)
#### Post date: [20 September 2024 17:11 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/8 "2024-09-20T17:11:25Z")
> [@E1cid](#):
>
> ```auto
> {
> "entity_id": "light.living_room_main_light_light",
> "brightness": globalContext("brightness")
> }
>
> ```
many thinkas , this was what I needed , It's all working now 🙂
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [4 October 2024 17:11 UTC](https://discourse.nodered.org/t/using-a-global-variable-in-the-data-json/91145/9 "2024-10-04T17:11:26Z")
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