JS code can be a pain to maintain (in the membrane... joke, sorry, I'll stop). And FB knows this. That's why they developed ReasonML: great JS interop, but much

JS code can be a pain to maintain (in the membrane... joke, sorry, I'll stop). And FB knows this. That's why they developed ReasonML: great JS interop, but much better maintenance story (than both JS and TS) because of the stronger typing discipline. On a large code base, increased maintainability can be a huge commercial advantage.