Ya, I would probably be happy with TypeScript. How's the backend story? Is using it with node easy? Is there an interactive mode, or just quick transpilation?
tsc --watch
There's also an REPL for Node here: https://www.npmjs.com/package/ts-node
I find it a bit tricky to do anything complex in, though. Since TypeScript is mostly ES2015 anyway, when I want interactive anything I usually just use an ES2015 interpreter (like Node itself). The types usually make interactive stuff more challenging.