Is this a valid monad transformer in Javascript?

Question

In order to better understand monad transformers I implemented one. Since Javascript is dynamically typed I don\'t mimic type or data constructors but declare only plain old

Answer 1

Is the cause of this problem that the way I apply chain is wrong?

Yes. You need to pass an mf that returns an arraym, not an array like addm does. You could use

const addmm = x => y => array.map(maybe.of)(addm(x)(y))
arraym.chain(x => arraym.chain( addmm(x) )(arrayOfMaybes))([[10]])

To help with this, you also might consider implementing lift for every monad transformer.