There is no way, currently, to deduce vanilla javascript types. You'll have to write your own bindings (types) or as you pointed out, use community bindings on

There is no way, currently, to deduce vanilla javascript types. You'll have to write your own bindings (types) or as you pointed out, use community bindings on redex. Now? Writing a binding is barely a speed bump, but when I first started writing Reason code it definitely tripped me up a few times. I tried to make the road behind me a bit smoother [1], but that gap you observed is real. But as someone who writes/reviews both Typescript and Reason, pretty much every day, there is space for both projects, so I don't see that gap as being relevant to the survival of Reason--rather, its something that with hard word will be improved over time.