You can absolutely use Dart instead of Javascript, but that's because Dart 1.0 has been released, and because Dart compiles to Javascript. The standardization

You can absolutely use Dart instead of Javascript, but that's because Dart 1.0 has been released, and because Dart compiles to Javascript. The standardization means that the spec will be ratified, a conformance test suite will be created for independent implementations, and a process for evolving the language will be developed. It means that we can can compatible implementations, and that other individuals and companies interested in participating in the evolution of Dart will have an opportunity to do so.