Hi @andre_x Where does it tell you that there is an error?
In a debug node? can you share a screenshot of the error?
Or in the node itself? if so, hovering over the red triangle should show the type of error, you can share it.
it would also help if you shared your flow.
There would have been a little red line under the error in the code window, but that can be difficult to see. However, it also shows a red marker in the scroll bar on the right hand side where the error is, so if you have a problem then look for that and you should be able to see where the problem is.
Strictly, you should use const there since it shouldn't ever be replaced. You can still add to a const object or update its properties - same for a const array.
Apologies for extending the side-conversation - I'll shut up after this - promise!
The reason for using const is to avoid more subtle errors and force them out early. Since trying to replace a const variable will raise an error. They can be a really useful thing in more complex code and personally, I train myself to try to use best practice in the easy stuff so that the more difficult bits aren't so painful.
But of course, in short snippets of code that most people will use in a function node, this really won't make a tremendous amount of difference.