Expose Dart functions to javascript

Question

I'm a bit of a newb to dart, and trying to get my feet wet by writing some library functions in it.

While I've had no problem calling javascript functions from dart, I'd love to be able to call dart functions from javascript, but so far, I'm not having much like.

For example, I'd love to be able to expose some basic functions from dart, for example like so:

main() {
  String foo() {
    return "bar!";
  }

  js.scoped(() {
    js.context.foo = foo;
  });
}

and then be able to call them from javascript, like so:

<script>
  window.onload = function() {
    alert("foo() = " + foo());
  }
</script>

Is something like this even possible?

Answer 1

No problem ! see Calling Dart from JavaScript.

In your case :

import 'dart:js' as js;
main() {
  String foo() {
    return "bar!";
  }

  js.context['foo'] = foo;
}

Answer 2

In Dart 1.20 I had to add allowInterop()

import 'dart:js' as js;
main() {
  String foo() {
    return "bar!";
  }

  js.context['foo'] = allowInterop(foo);
}

Answer 3

In Dart 2.3.0 I had to tweak the solution just a bit for allowInterop to play nice.

    import 'dart:js' as js;
    main() {
      String foo() {
        return "bar!";
      }

      js.context['foo'] = js.allowInterop(foo);
    }