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How to invoke a function generated by js_of_ocaml?
Asked Answered
javascriptocamljs-of-ocaml
S

1

8

I am new to JavaScript, I am trying to use js_of_ocaml.

I first wrote a very simple cubes.ml:

let simple (a: int) =
  a + 1234

Then complied it:

ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax \
          -syntax camlp4o -linkpkg -o cubes.byte cubes.ml

then generated the JavaScript file:

js_of_ocaml cubes.byte

Here is the generated cubes.js. Note that we could not find 1234 or function name simple in that file.

I have another JavaScript file Home.js, where I want the function callSimple to call what was generated in cubes.js. But I don't know how to write it. Could anyone help?

(function () {
    ...
    function callSimple(a) {
        return ???;
    };
    ...
})();

Edit 1:

I tried the solution proposed by @EdgarAroutiounian :

(* cubes.ml *)
let () =
  Js.Unsafe.global##.jscode := (object%js
    val simple = Js.wrap_meth_callback
        (fun a -> a + 1234)
    val speak = Js.wrap_meth_callback
        (fun () -> print_endline "hello")
  end)

It did compile, but it did not return the right output: enter image description here

If I write in home.js:

confirm(jscode.simple(10)); // 1244 is expected
confirm(jscode.speak()); // "hello" as string is expected

the first line returns function (a){return p(c,aM(b,a))}, and the second line returns 0. They are not what I expect.

Scleroderma answered 6/5, 2016 at 13:7 Comment(0)
C
6

Here's one possible way to do it.

In our OCaml code intended to be exposed to JavaScript:

let () =
  Js.Unsafe.global##.jscode := (object%js
    val simple = Js.wrap_meth_callback
        (fun a -> a + 1234)
    val speak = Js.wrap_meth_callback
        (fun () -> print_endline "hello")
  end)

Notice that I'm using the ppx extension, I recommend you do so as well: this means no more camlp4. You can compile that code with:

ocamlfind ocamlc -package js_of_ocaml.ppx -linkpkg cubes.ml -o T
js_of_ocaml T -o cubes.js

Then in your other file, home.js

console.log(jscode.simple(10));
console.log(jscode.speak());

and an index.html of: 

<!DOCTYPE html>
<meta charset="utf-8">
<body>
  <script src="cubes.js"></script>
  <script src="home.js"></script>
</body>

And that should work.

Crowned answered 7/5, 2016 at 5:5 Comment(4)
@antonrov your suggested edits are wrong and change the semantics of the post. – Crowned
I guess you are referring to me... Could you, please, elaborate on your intended semantics? It would be nice if you specified what we should see in the console. – Daly
@EdgarAroutiounian What you suggested did compile, but the output is not what I expect. Please see my updated OP... – Scleroderma
@Scleroderma Can you show the full code? What is the expected output? The 0 is coming from console.log. – Crowned

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