> I'm glad to hear that, but the fact that it is possible to just not serve the JS (or, just as badly, not test it: from what I've read elsewhere in this thread

> I'm glad to hear that, but the fact that it is possible to just not serve the JS (or, just as badly, not test it: from what I've read elsewhere in this thread, the semantics of Dart2JS is not the same as the semantics in the Dart VM!) doesn't give me confidence that people won't write Web apps that depend on the Dart VM. > The worry is that Web apps will come to depend on the Dart VM being present. I have seen nothing to indicate that this is not a very real possibility. Dart has always their primary goal to compile to efficient JavaScript: > For languages that are quite different from JavaScript: it's important for Dart to compile to efficient JavaScript - http://www.dartlang.org/support/faq.html#compare-to-everything-else http://www.dartlang.org/support/faq.html#compare-to-everythi... There have been many times where language features were dismissed because they couldn't be compiled to efficient JavaScript (e.g. non-local returns and tail recursion). Google knows that Dart2JS is an important platform to optimize for (which has great source maps / debugging and tree-shaking optimizations) since it's the platform target that most browsers will be running and they want to ensure their own internal apps built with Dart2JS has a good experience across all browsers. Following the mailing list, the only known deviation (that's wasn't a bug) is with some corner cases involving its use of arbitrary-precision integers: http://www.dartlang.org/articles/numeric-computation/ http://www.dartlang.org/articles/numeric-computation/ which relates from numbers in JS being stored in doubles (IEEE-754). Other than that it's impossible for web developers to "target the Dart VM", the libraries in the Dart SDK are separated by platform so packages that can only run on the Dart VM like 'dart:io' cannot run on the client. Likewise there are some client packages like 'dart:html' that can only run in a browser and not on the server.