There's a fair bit of work in this area that leverages Flow type syntax, e.g:

- https://github.com/gcanti/tcomb

- https://github.com/gcanti/io-ts (for typescript)

- https://github.com/codemix/flow-runtime (i wrote this)

And another alternative is to use Design by Contract, like Eiffel:

https://github.com/codemix/babel-plugin-contracts (also me)