Just for the record I'm not saying Dart is amazing and everyone should use it, all I'm saying is that we should evaluate it objectively. If raw speed is your bottleneck then why are you wasting time evaluating Dart? Nobody is forcing anyone to use it, you can ignore it and move on with your day.
Underscore.js and Backbone.js put together are 1/8th the size of HelloDartTest.dart.app.js.
jQuery plus dozens of jquery.ui plugins can come close in size, but that actually does a lot. This boilerplate doesn't seem to have much functionality in it.
The problem here, and what is making us chuckle so much, is that the project as presented to us is not magical. For whatever reason, some of the brightest minds in our industry have not presented us (at this time) with a cross-compiler that is both robust enough to support large apps, and intelligent enough to self-optimize its output.
I wonder where this is on the path to the singularity?
I moved things around so that what code does is roughly equivalent. As you can see Dart is slower, but the Dart runtime does not differ by a margin that matters for many applications - and note the size of the gap differs significantly between JS engines.
print$getter()(1, $noargs, 'Hello, Dart!');
print$getter()(1, $noargs, 'foo');
print$getter()(1, $noargs, 'bar');