# Scope of constants
**URL:** https://discourse.nodered.org/t/scope-of-constants/97629
**Category:** General
**Created:** [15 June 2025 06:38 UTC](https://discourse.nodered.org/t/scope-of-constants/97629 "2025-06-15T06:38:26Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@Janvi](https://discourse.nodered.org/u/Janvi)
#### Post date: [15 June 2025 06:38 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/1 "2025-06-15T06:38:26Z")
if I define any constant like
const value = {val:123};
its only known inside same node. Is there any possibility to put this definition to flow-scope without using context variable by flow.set ?
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### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [15 June 2025 07:08 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/2 "2025-06-15T07:08:40Z")
Probably the preferred Node-red way is to attach the value as a message property, thus ensuring it is available in every node of the flow.
You can (if you must 🤠) set environment variables for the flow.
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 June 2025 07:33 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/3 "2025-06-15T07:33:08Z")
can you describe the use case / provide a couple of examples of how you would use this constant?
I suspect environment variables are the right choice but you might not realise the various levels they can be set and how to utilise them in your flows.
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### Author:  [@Janvi](https://discourse.nodered.org/u/Janvi)
#### Post date: [15 June 2025 09:21 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/4 "2025-06-15T09:21:24Z")
The constant definition is simply to make the code more readable and better maintainable for humans. Dont wonder about my odd question - as C and assembly programmer I am cought in too much concerns about the code performance.
Its always possible to take a variable with flow.set or pass as parameter to the next node what probably uses the stack. I must not take care that constants are not variable and never change. Obviously, the JIT compiler works completely diffrent to other language compilers, there is nothing like a preprocessor and I simply have to trust node.js. Im am going to try the env variables @jbudd suggested (although constants are not variable).
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 June 2025 09:38 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/5 "2025-06-15T09:38:14Z")
> [@Janvi](#):
>
> env variables @jbudd suggested (although constants are not variable).
Yeah I've always found the name a little curious. Environment variables are 100% not variable 😂
Perhaps they should be renamed environment constants 🤔
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 June 2025 09:40 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/6 "2025-06-15T09:40:01Z")
Ps, there are some useful tips on various ways env vars can be used in unexpected ways in the docs: [Using environment variables : Node-RED](https://nodered.org/docs/user-guide/environment-variables)
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### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [15 June 2025 10:03 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/7 "2025-06-15T10:03:51Z")
> [@Janvi](#):
>
> The constant definition is simply to make the code more readable and better maintainable for humans.
> [@Janvi](#):
>
> the env variables @jbudd suggested
"suggested" is a bit strong. I think that the way environment variables are implemented in Node-red offers confusion over immutable "variables" and boundless scope for subtle bugs.
Which approach gives more easily maintainable code?
```auto
// embedded magic numbers are very very bad
let energy = msg.mass * 90000000000000000
// Environment variables are very bad.
// Where was this environment variable declared = node / group / flow / environment file / settings.js / operating system?
energy = msg.mass * env.get("csquared")
// global context variables are quite bad (except for real physical constants)
energy = msg.mass * global.get("csquared")
// msg.properties are easier to track down
// where did msg.csquared get a value?
energy = msg.mass * msg.csquared
```
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### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [15 June 2025 15:59 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/8 "2025-06-15T15:59:41Z")
But note that a constant referring to an object, such as
`const value = {val:123}`
Is a constant reference to an object, not a reference to a constant object. That means that one cannot then write
`value = 3`
But one _can_ write
`value.val = 7`
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### Author:  [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)
#### Post date: [15 June 2025 23:09 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/9 "2025-06-15T23:09:36Z")
> [@Steve-Mcl](#):
>
> Yeah I've always found the name a little curious. Environment variables are 100% not variable 😂
>
> Perhaps they should be renamed environment constants 🤔
Urm, env variables absolutely ARE variable - just not always inside an app. They are certainly variable at the OS/shell level. Which, of course, is where they originated.
Unfortunately, they are not variable inside a node.js app.
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### Author:  [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)
#### Post date: [15 June 2025 23:13 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/10 "2025-06-15T23:13:08Z")
> [@Colin](#):
>
> Is a constant reference to an object, not a reference to a constant object
And using objects in context variables can also solve one of jbudd's gripes - what set the data? Simple, just add another property and record that when you write it. I do this regularly for the reason mentioned.
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### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [13 September 2025 23:13 UTC](https://discourse.nodered.org/t/scope-of-constants/97629/11 "2025-09-13T23:13:53Z")
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