Returning an array from Javascript (RuntimeError: unreachable)

[HildingElmqvist]

I want to allow entering the initial conditions in the web app. I thus want to call a Javscript function which returns a vector from Julia: `

  function getInitial() {

    return [5.0, 6.0, 7.0]  

  }

`

I declared the return type as Externref: initial = @jscall("getInitial", Externref, Tuple{}) I added some logging:

`

JS.console_log("initial")

JS.console_log(initial)

JS.console_log("initial[1]")

JS.console_log(initial[1])

JS.console_log("Done")

`

I am not able to pick up the first element of the vector. I get:

`

initial

(3) [5, 6, 7]

initial[1]

lorenz.wasm:0xd2 Uncaught RuntimeError: unreachable

at lorenz.wasm:0xd2

at run ((index):88:16)

at async (index):90:15`

Is this supposed to work or is there any work around?

[tshort]

The Externref isn't directly usable within Julia. You can only pass it back to JavaScript. You should be able to call JS._get(initial, 1, Float64) to extract an element from the JS array.

Wait. There's an easier way. You should be able to get that array in Julia with Vector{Float64}(initial).

Let me know if that doesn't work.

[HildingElmqvist]

Thanks for your quick suggestions!

No, Vector{Float64}(initial) did not work. The compilation script returns too quickly without any error message.

JS._get(initial, 2, Float64) works. Is there a way of getting the size of the array or I have to query that separately?

[tshort]

Try:

n = @jscall("x => x.length", Int32, Tuple{Externref}, jsa)

I need to fix and add a test case for Vector{T}.

[HildingElmqvist]

n = @jscall("x => x.length", Int32, Tuple{Externref}, jsa) worked fine.

Thanks a lot!