TypeScript has to handle every JavaScript quirk, it puts structure in place to help mitigate many issues. ReasonML breaks from full compatibility, it can pick

TypeScript has to handle every JavaScript quirk, it puts structure in place to help mitigate many issues. ReasonML breaks from full compatibility, it can pick and choose JavaScript features to compromise between familiarity and functionality. At the other extreme you have Elm, which has a similar background but won't compromise so can offer a clean break from JavaScript.