How can I store "contextual" data (associated with a single chain of function calls) in Kotlin/Javas...

# javascript

[Norbi]

How can I store "contextual" data (associated with a single chain of function calls) in Kotlin/Javascript in the browser?
In Kotlin/Java I use ThreadLocal and ThreadContextElement but I struggle to find a good alternative in Kotlin/Javascript.
As usual, I started to make all of my functions suspend (because it is "viral" anyway) but if I call a non-suspend library function the context is lost.
Thanks.

[Robert Jaros]

JS is single-threaded. The whole app is just single chain of function calls 😉

[Norbi]

I know :]
But maybe you know what I mean, like a Javascript alternative to MDC in logging? Is the only solution to pass around info in function parameters?

[Robert Jaros]

As there is always one thread, I think you can just use a global variable instead of ThreadLocal.

[Robert Jaros]

Initialize your context in some place, put it in the variable and it will be valid until some new part of code is executed where some other context is initialized and saved.

[Robert Jaros]

But it could probably work with non-suspend functions only.

[Norbi]

It know it is single-threaded but there are multiple task running at the same time.
Like one task is updating the UI, some other is making a network call and waiting for the result, another is waiting for a timer to expire.
These are separate "threads of execution", and I would like to find a solution to implement for example MDC in logging.
(I know this is a theoretical question but I'm curious what are the alternatives besides passing the info in parameters - suspend functions do this as well, they pass the continuation as a parameter.)

[Edoardo Luppi]

You can associate data using coroutine scopes if I'm not mistaken.
I don't recall the details, but in case ask in #coroutines

[Edoardo Luppi]

@Norbi curious if you managed to find a reasonable approach

[Norbi]

I already use CoroutineContext and it's OK for me because my app is Kotlin-only.
I was just curious that JS really doesn't have an alternative built-in solution.
I have read about:
• _async_hooks_ (node.js-specific)
• https://www.npmjs.com/package/zone.js
• https://github.com/vlcn-io/model/tree/main/ts/packages/zone