What is (and isn't) converted from Elixir to Javascript?

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Hi All

Just started looking at Hologram and think it has huge potential. Is there a list of what does, and doesn’t work when converting from Elixir to JavaScript. I was looking to validate that a form field was a valid number and had the following

elixir

case Integer.parse(params.event.value) do

      {int, _} -> int

      :error -> :error

end:


```

When running the code I get the following error in the console:

runtime.entry.js:364 Uncaught HologramBoxedError: (FunctionClauseError) no function clause matching in Integer.count_digits/2

The following arguments were given to Integer.count_digits/2:

    # 1
    "1"

    # 2
    10

I’m assuming this is because Integer.parse doesn’t yet convert to JavaScript. Of course I could be completely wrong and this is a silly error on my part.

cheers

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deleted: Too fast, too furious.

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Is that me or you :slight_smile:

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Hey @dbsimmons64,

Elixir functions are transpiled automatically to JavaScript by Hologram. However, at the very bottom layer, they use Erlang functions which need to be ported by hand to JavaScript. The detailed process is described here: Hologram Elixir -> JS compilation - #6 by bartblast

If some Erlang function isn’t yet ported, an error with details about the missing function is displayed in the browser console. However, that’s not what you encountered here.

The error you’re seeing with Integer.count_digits/2 was due to problems with bitstring segments handling in the client-side implementation. However, even after fixing that initial bitstring handling issue, you would have eventually encountered errors about missing Erlang function ports that Integer.parse/2 depends on. So there were actually two layers of problems: first the bitstring patterns handling, and then missing Erlang functions underneath.

Good news:

I’ve just released v0.6.3 that fixes the client-side support of Integer.parse/2. Both the bitstring handling issues and the missing Erlang function dependencies have been resolved, so your code should work now after updating.

Current project stage:

At this stage of the project, if something doesn’t work it’s usually a small thing and I typically fix it within 24 hours - just like with your issue!

Going forward:

I completely agree - we need more transparency about which Erlang functions are missing. I’ve been thinking recently about creating some initiative to help me port the rest of the functions. The process is actually quite simple, especially with the help of AI tools (it’s a perfect use case for them), but it’s time-consuming for me as I’m juggling many other aspects of the project like new features, core functionality, etc.

If you’re interested in helping with Hologram development, porting these Erlang functions would be the perfect way to contribute! Each function is relatively straightforward to implement, and I’m happy to review pull requests and provide guidance.

2 Likes
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Thanks so much @bartblast for the detailed explanaition. I’ll take a look at the link you’ve provided to see if I can better understand the process (if so I’d love to help out). Cheers.

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