Primitives

Below the subsystem layer there is a set of foundational types every subsystem uses. They are not user-facing — they live in src/ and lib/internal/ — but understanding them makes the rest of the codebase legible.

Pages

• Environment and Realm — node::IsolateData, node::Environment, node::Realm. The C++ data structures that own a Node instance.
• BaseObject and BindingData — BaseObject, BaseObjectPtr<T>, BaseObjectWeakPtr<T>, the per-binding BindingData struct, and how all of this survives snapshots.
• AsyncWrap, HandleWrap, ReqWrap — the libuv ↔ JS plumbing that backs every async resource.
• Builtins, primordials, and snapshots — how lib/**/*.js gets compiled into the binary, frozen, captured into a V8 snapshot, and replayed at startup.

For higher-level subsystems that build on these, see Systems.