Calling Rust from NodeJS

The short answer: you cannot export any Rust function for FFI bindings, you need to specifically export Rust functions compatible with C.

Specifically, this means that you need to expose only C-struct compatible objects OR expose opaque pointers (which can only be manipulated through Rust functions).

In your case, Vec<Post> is not compatible with usage in FFI, because Vec is not.

You can find more information in the FFI Guide.