JavaScript variables are not being registered outside of cells

[IntegerMan]

Describe the bug

Apologies if this is a misunderstanding of kernel limitations.

I can import a C# variable into JavaScript without issues. However, if I declare a JS variable in a JS cell using either let or const, that variable does not seem to be registered in the variables section, is not available in the next cell (even if it's a JS cell), does not share correctly to C# or other kernels, and perhaps most interestingly, doesn't log out at the end of the same cell it was defined in if it was the closing value as in:

let jsVar = 42;
jsVar; // jsVar is not displayed after the cell

JavaScript otherwise appears to function just fine, but variable persistence and sharing just isn't working for me.

See https://github.com/IntegerMan/PolyglotNotebookTalk/blob/main/cs_js.dib for my sample notebook.

Please complete the following:

Which version of .NET Interactive are you using? (In a notebook, run the #!about magic command. ):

• OS
  • Windows 11
  • Windows 10
  • macOS
  • Linux (Please specify distro)
  • iOS
  • Android
• Browser
  • Chrome
  • Edge
  • Firefox
  • Safari
• Frontend
  • Jupyter Notebook
  • Jupyter Lab
  • nteract
  • Visual Studio Code
  • Visual Studio Code Insiders
  • Visual Studio
  • Other (please specify)

Screenshots

[jonsequitur]

This is by design. The JavaScript kernel executes your code submission within a function, and so variables declared in that function scope aren't visible (including for variable sharing) outside unless you use this syntax:

x = 123;

By not using the let, const, or var keywords with your variable declaration, you're enabling JavaScript variable hoisting to make the variable visible to other cells (i.e. within other functions in the top-level scope).

As for return values from JavaScript cells, the trailing expression syntax isn't supported in JavaScript. So while in C# Script, this is equivalent to a return statement:

123

in JavaScript you need to write this:

return 123;

[IntegerMan]

Thank you so much for the reply @jonsequitur. I'll play around with that tonight!

[jonsequitur]

Looking forward to your thoughts. I'll update the docs with these details because it's unintuitive.

[jonsequitur]

I'll keep the issue open for now and close it once the docs are updated.

[IntegerMan]

I'd also put it in the FAQ as I checked that for this along with the kernels overview before opening the issue.

[IntegerMan]

So I've been playing with this and if I do:

let jsVar = 42;
return jsVar;

I do see the value 42 after the cell, which is good, but no variable sharing occurs either. Is variable sharing just not possible between different JS cells in Polyglot?

[colombod]

let / const / var are scoped to the evaluation. to make them globally visible do

jsVar = 42;
return jsVar;

the jsVar will then be visible in variable explorer too