Varity is a lightweight Node.js utility that wraps functions to automatically handle variable‑arity arguments. By declaring expected parameter types (via constructors, arrays or concise one‑letter strings) and optional flags, it normalizes missing, optional or out‑of‑order arguments, supplies sensible defaults, and can extend or validate them—saving developers from repetitive type‑checking boiler‑plate. It’s aimed at JavaScript developers who write APIs or callbacks that accept flexible argument lists.