As far as type systems/language features: TypeScript: - Structurally typed - Enum types - Mapped types - Abstract classes - Scoped class members (public,

As far as type systems/language features: TypeScript: - Structurally typed - Enum types - Mapped types - Abstract classes - Scoped class members (public, private, protected) - Namespaces Flow: - Nominally typed - Covariance/contravariance annotations - Supertype annotations (via $Supertype type) - Subtype annotations (via $Subtype type) - Arity annotations (via $Pred type) - Subtraction types (via $Diff type) - Opt-in 2-way type resolver (via * type) - Refer to nested type (via $PropertyType type) Otherwise, the two are remarkably similar. I've been using TS for a few years, and Flow for a few months. Please correct me if any of the above are wrong.