None value is not coverted to null in JavaScript.

I don’t know if this is a bug but I have code like this (that use jQuery Terminal library):

from browser import window, alert

def interpreter(command, term):
    term.echo(">>> " + command)

window.jQuery("body").terminal(interpreter)

and I have exception in JavaScript because None value returned by interpreter is a cycle that can’t be used in JSON.stringify because In jQuery Terminal the value returned by the function is processed and echoed in terminal (It can be a string or a promise). Is there a way to convert None to null or undefined to be used in JavaScript or return undefined/null from javascript?

I’ve fixed the issue by wrapping terminal function invocation and wrap interpreter with function that don’t return anything, but it would be nice if Brython convert None to null in python functions.

I’m using stable version from github.

[PierreQuentel]

In the commit referenced above I have added 2 new constants in built-in module javascript, called NULL and UNDEFINED, set to Javascript values null and undefined. They can be returned by a Brython function used by a Javascript library that handles these values.

I tried this code in a page with the Terminal library :

from browser import window
import javascript

def interpreter(command, term):
    term.echo(">>> " + command)
    return javascript.UNDEFINED

window.jQuery("body").terminal(interpreter)

I don’t know if the program does what is expected, but at least it doesn’t crash 😉

Does this help ?

[PierreQuentel]

As Jonathan said, it’s not possible for a function to know if it’s called from Brython or Javascript. And anyway, there must be a way to return either null or undefined (I saw that jQuery Terminal doesn’t handle these values the same way).

Can the issue be closed ?