[jmesserly]

> How well does Dart interact with JavaScript, especially libraries that are asynchronously loaded? I know that the Dart compiler is a whole-program optimizer, and I get the impression that Dart wants to own all the code on the page.

Great question. Generally dart:js will let you do interop: https://www.dartlang.org/articles/js-dart-interop/. It's designed to interact pretty well with the dart2js compiler. However it feels a lot like you're using a foreign function interface. For example, calling a the global method Object.keys is: js.context['Object'].callMethod('keys', [obj]);

For Custom Elements (one of the new web components specs) we did something better: you can register the Dart wrapper type associated with that element. Then whenever you get one of those elements, it automatically looks like the Dart type. We used this heavily in the new core_elements and paper_elements packages. Here's an example of defining a type like that: https://github.com/dart-lang/core-elements/blob/master/lib/c...

Ultimately we'd like to make something similar for all JavaScript objects and expose it from dart:js. That would make interop almost seamless (especially if we could generate the types from DefinitelyTyped's APIs).