JavaScript will always convert a value to a type. It's dynamic, but very strongly typed. JavaScript engines do not care about type annotations, only TypeScript does. You might have annotated something as a number, but the JavaScript engine might chose to convert it to a string ... I think type annotations is a unnecessary chore, and that types should be inferred.

Types cannot be inferred in dynamic typing systems. That is the whole point of dynamic type systems: type might change during runtime.