Dart is a platform play influenced by Javascript with some JS interop, but mostly requires its own new libraries and ecosystem, which allows many things to be fixed.
Typescript is a layer on top of Javascript and existing Javascript libraries that adds hybrid/latent typing. Typescript doesn't require a new ecosystem, but instead allows enhancements to the existing one.
Both approaches are valid.
(Disclaimer: MS employee, but had this discussion with Gilad a few weeks back)
>Typescript is a layer on top of Javascript and existing Javascript libraries
With all horrible issues JS has: unpredictable perf, library hell.
Also my issues with TS are:
1) what if future ECMA will bring incompatible changes with current TS ? TS will break compatibility or we will have another EEE from MS ? Dart clean break seems like a safer approach.
2) there is no cross-platform IDE for TS (yea I know plugins - but Dart has stock cross-platform IDE)
Typescript is a layer on top of Javascript and existing Javascript libraries that adds hybrid/latent typing. Typescript doesn't require a new ecosystem, but instead allows enhancements to the existing one.
Both approaches are valid.
(Disclaimer: MS employee, but had this discussion with Gilad a few weeks back)