[phi-y]

>> - There is no hard guarantee at runtime as everything is partially/optionally typed (including your deps).

Most typed languages don't have hard guarantees at runtime. With java, using reflection you can do all kinds of weird things at runtime. C++ has fewer guarantees because there is no VM and can't even introspect objects to see their real type. Dependencies are a real issue with TS, but many libraries are written in typescript and the type files are really robust.

>> The types are not used to produce faster code at runtime (like in a compiled language).

The V8 intepreter will actually do this at runtime. Usually it takes less than a second for v8 to optimize the javascript, and it will recognize that many functions and objects use the same interface and optimize appropriately. If you think about it the types only help so much because once you have the code graph, it becomes really easy to find the type and optimize the memory layout.