Basically what you are looking for is V8 Templates. It exposes all your C++ code as JavaScript functions that you can call from within the V8 Virtual Machine. You can associate C++ callbacks when functions are invoked or when specific object properties are accessed (Read Accessors and Interceptors).
I found a very good article which explains all of this – How does NodeJS work?. It also explains how libuv works in conjunction with Node to achieve asynchronicity.
Hope this helps!