# How to delete a flow variable from a \`function\` node
**URL:** https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731
**Category:** General
**Created:** [30 December 2019 09:06 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731 "2019-12-30T09:06:45Z")
**Posts on this page:** 17
**Page:** 1
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [30 December 2019 09:06 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/1 "2019-12-30T09:06:45Z")
I know........ Use the `change` node.
Please indulge me.
In one node I have:
`flow.set('example',"something");`
How do I delete the _flow_ variable called example?
`delete flow.example` doesn't work.
Stuck.
---
### Author:  [@afelix](https://discourse.nodered.org/u/afelix)
#### Post date: [30 December 2019 09:08 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/2 "2019-12-30T09:08:57Z")
It’s not the most logical approach, but with some understanding of core JavaScript/core Node-RED logic it makes more sense: by setting it to `undefined`.
`flow.set('example', undefined);`
---
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [30 December 2019 09:25 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/3 "2019-12-30T09:25:48Z")
Tried....
```auto
let x = flow.get('TRAIN');
if (x == 'HELD')
{
msg.payload = "TRIP";
msg.topic = "TRAIN";
flow.set('TRAIN',undefind);
return msg;
}
```
```auto
ReferenceError: undefind is not defined (line 6, col 22)
```
Doesn't work.
---
### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [30 December 2019 09:38 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/4 "2019-12-30T09:38:00Z")
Maybe try spelling it as was shown ?
---
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [30 December 2019 09:42 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/5 "2019-12-30T09:42:00Z")
Thanks.
I worked around it and made it `null` rather than `undefined`
---
### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [30 December 2019 09:51 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/6 "2019-12-30T09:51:56Z")
That’s not a work around. That defines it as null. So it still exists.
---
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [30 December 2019 09:54 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/7 "2019-12-30T09:54:06Z")
Oh.
Well, from the code I posted, it simply needs to not be `HELD`
But I may change it to undefined.
(I think the parser was stuffed up because I was doing it via audio and it messed up the fined/find part)
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [30 December 2019 09:54 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/8 "2019-12-30T09:54:20Z")
The error was that you had spelt it undefind instead of undefined. Hence the error message "undefind is not defined"
Of course undefined is not defined also, but in this case would not throw an error.
---
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [30 December 2019 09:56 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/9 "2019-12-30T09:56:16Z")
Colin, I agree and just admitted it.
The problem was the `find` part.
Rather than `fined` it was parsed as `find`.
Parsed by me.
---
### Author:  [@afelix](https://discourse.nodered.org/u/afelix)
#### Post date: [30 December 2019 09:57 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/10 "2019-12-30T09:57:07Z")
Because sometimes a picture says more than a thousand words:
`null` is the _assignment_ of the value “nothing” to a variable. `undefined` the _declaration_ of a variable without a value.
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### Author:  [@krambriw](https://discourse.nodered.org/u/krambriw)
#### Post date: [30 December 2019 13:03 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/11 "2019-12-30T13:03:14Z")
Lovely!!!!
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### Author:  [@krambriw](https://discourse.nodered.org/u/krambriw)
#### Post date: [30 December 2019 13:06 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/12 "2019-12-30T13:06:04Z")
@dceejay
I know...xmas is over...but is there also New Year Gifts available?
Kind regards, Walter
# [Working with context in function nodes](https://discourse.nodered.org/t/working-with-context-in-function-nodes/19567)
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [30 December 2019 13:19 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/13 "2019-12-30T13:19:26Z")
We have an item on the backlog to add a delete function to the context API. It sits there alongside everything else that waits for someone to do.
https://trello.com/b/R0O3CSrI.html
---
### Author:  [@krambriw](https://discourse.nodered.org/u/krambriw)
#### Post date: [30 December 2019 13:34 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/14 "2019-12-30T13:34:10Z")
Oh, I see, well with the very well illustrated explanation given about null & undefined, the work around is working great (used it myself) so there is no real urgency I think
Anyway, I would then like to take the opportunity, to thank everybody for a great NR year and wish all a Happy New (NR) Year to come
---
### Author:  [@iOnline247](https://discourse.nodered.org/u/iOnline247)
#### Post date: [31 December 2019 06:22 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/15 "2019-12-31T06:22:19Z")
Is there a contribution guide I can follow? We're looking to use Node-RED for some of our ESB services and I'd like to pitch in where I can.
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### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [31 December 2019 08:36 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/16 "2019-12-31T08:36:24Z")
See [https://github.com/node-red/node-red/blob/master/CONTRIBUTING.md](https://github.com/node-red/node-red/blob/master/CONTRIBUTING.md)
---
### Author:  [@JARLEIGUIMARAES](https://discourse.nodered.org/u/JARLEIGUIMARAES)
#### Post date: [16 December 2020 17:31 UTC](https://discourse.nodered.org/t/how-to-delete-a-flow-variable-from-a-function-node/19731/17 "2020-12-16T17:31:05Z")
It works fine. Thx!👊