This code illustrates the private state with controlled access pattern: 1) The config object is private to the module, not exported directly, 2) Access to config is only through controlled getter and setter functions, 3) The getter returns a copy to prevent direct mutation of internal state, 4) The setter accepts a new configuration and creates a fresh copy, 5) This pattern provides encapsulation of module state while allowing controlled access, 6) It prevents accidental modifications to the internal state, 7) It's a common pattern for managing module-level configuration or state.