I have a few projects written on Typescript.
TS has a declaration files (d.ts) to declare non-ts libs. How it's works in Dart?
Dart looks very cool but I'd like to use Backbone and Marionette in my project.
Is there opportunity to rewrite projects at Dart or use Dart in next project using Marionette?
There are some attempts or plans to support that better but currently I guess this isn't too easy.
dart:js provides support to call between Dart and JS but this probably won't work with d.ts. You'd need to rebuild d.ts for dart:js.
Support for d.ts seems to be work in progress and a first version should become available in the not too far future https://github.com/dart-lang/sdk/issues/23423
The dev_compiler team is working on generating TypeScript output from Dart code https://github.com/dart-lang/dev_compiler/issues/397. I don't know about the status. Seems to be farther away.