Yes and no, An important caveat that Dart as JavaScript runs in it's own isolate and communicates with existing JavaScript libs through ports. This js-interop code is nearly 500k unminified. And you won't be able to minify all your JS (dartJs + other js) into one lib, because dart js doesn't play well with standard tools. One can certainly interop with js libs, but it's not pretty. Dart is not near 1.0 yet, so there is still time for improvement, but this doesn't seem to be a priority. Dart is great, don't get me wrong, and I've been working with it for several months, but I think this point should be made in fairness. You're really going to want to go all in with Dart and leave your custom js libs behind or convert them to Dart. If you have the luxury of working with just Dart code, then you'll be in for a pleasant surprise at how productive you can be and how fast the Dart VM is.