I understand Dart compiles to JavaScript, and I read the Dart Language Spec on Libraries, although I didn't see an answer there. Also a search on their discussion form for the word 'existing' turns up 3 results that are not related.
Does anyone know if Dart will support the use of existing JavaScript libraries such as jQuery or Raphael?
The answer is now Yes! Dart now ships a JS-interop library to use existing JavaScript code with your Dart app. Learn more here: https://www.dartlang.org/articles/js-dart-interop/