The State Machine Mental Model for UI Engineering

Every complex UI is secretly a finite state machine. Modeling that explicitly removes whole categories of bugs.

#The Hidden State Machine

Every UI has states: loading, error, empty, populated, editing, and saving. The question is whether those states are modeled clearly or hidden inside fragile if-else chains.

const machine = {
  idle: { FETCH: 'loading' },
  loading: { SUCCESS: 'populated', FAILURE: 'error' },
  error: { RETRY: 'loading' },
  populated: { REFRESH: 'loading' },
  empty: { REFRESH: 'loading' },
};

stateDiagram-v2
    [*] --> Idle
    Idle --> Loading: FETCH
    Loading --> Populated: SUCCESS
    Loading --> Error: FAILURE
    Error --> Loading: RETRY
    Populated --> Loading: REFRESH

• No impossible states: the UI cannot be loading and failed at the same time.
• Clear transitions: invalid movements are easier to catch.
• Visualizable logic: the model can be drawn and discussed before code exists.