The Finite State Machine pattern models a system as a finite number of states and transitions between them based on events, providing a predictable and robust way to manage complex UI states [citation:6].
The Finite State Machine (FSM) pattern is a behavioral model where a system can be in exactly one of a finite number of states at any given time. Transitions between states are triggered by events, and the output (what the user sees) depends on the current state. This pattern is particularly valuable for managing complex UI states (loading, success, error, empty) in components like data-fetching widgets, forms, and wizards. FSMs eliminate impossible states and make component behavior predictable and testable. Libraries like XState provide a powerful implementation, but the pattern can be applied with simple state variables [citation:6].