example of calling js from wasm ?

[jeromeetienne]

hello, im trying to learn how to call js function from assemblyscript.

is there a working example i could look at ?

thanks

[MaxGraey]

Hi, Jerome.
You can define functions inside typescript like:

main.ts

declare namespace console {
   function logi(val: i32);
}

// also you can do this
@external("env", "logf")
declare function logf(val: f64);

console.logi(123);
logf(1e10);

// if you not specify this via namespace of @external decorator external will be imported 
// with name of module i.e "main" in this case.

On javascript side you should write something like this:

index.js

WebAssembly.instantiateStreaming(fetch("build/main.wasm"), {
  env: {
    // import as @external("env", "logf")
    logf(value) {
      console.log("logf: " + value);
    },
    abort(msg, file, line, column) {
      console.error("abort called at main.ts:" + line + ":" + column);
    }
  },
  console: {
    // import as console.logi
    logi(value) {
      console.log("logi: " + value);
    }
  }
}).then(result => {
  // const exports = result.instance.exports
});

[MaxGraey]

Arguments which can be passed between JS <-> WASM is pretty limit it's just i32 and f64. For passing strings, arrays and etc you can use this package

[MaxGraey]

By the way after approved this PR AssemblyScript in WebAssembly Studio works again

[dcodeIO]

Closing this issue for now as it hasn't received any replies recently. Feel free to reopen it if necessary!

[trusktr]

For the life of me, I can't figure this out (well, short of diving into the AssemblyScript source code). I posted more details in #384

EDIT: As described in #384, I resorted to using @external syntax, and placed that in a separate file so as not to taint the other files with non-portable syntax.