Implement missing state machine transition logic

Hard

Implementing State Transitions in JavaScript State Machine with Event Handling

Implement the missing transition logic in this state machine:

Choose an option below

if (!currentTransitions[event]) {
    throw new Error(`Invalid event "${event}" for state "${this.currentState}"`);
}

const transition = currentTransitions[event];
const prevState = this.currentState;
this.currentState = transition.target;

if (transition.action) {
    transition.action(payload);
}

this.history.push({ from: prevState, to: this.currentState, event, payload });
this.subscribers.forEach(cb => cb(this.currentState, prevState));

const transition = currentTransitions[event];
if (transition) {
    this.currentState = transition.target;
    transition.action?.(payload);
}

const nextState = currentTransitions[event]?.target;
if (nextState) {
    this.currentState = nextState;
    this.history.push(nextState);
}

if (currentTransitions[event]) {
    this.currentState = currentTransitions[event].target;
    this.subscribers.forEach(cb => cb(this.currentState));
}

JavascriptClassesState machinesEvent handlingDesign patterns

1class StateMachine {
  constructor(initialState, transitions) {
      this.currentState = initialState;
      this.transitions = transitions;
      this.history = [];
      this.subscribers = new Set();
  }
8
  transition(event, payload = {}) {
      const currentTransitions = this.transitions[this.currentState];
      _______________________
      _______________________
      _______________________
      _______________________
  }
16
  subscribe(callback) {
      this.subscribers.add(callback);
      return () => this.subscribers.delete(callback);
  }
21}
22
23const machine = new StateMachine('idle', {
  idle: {
      START: { target: 'running', action: () => console.log('Starting...') },
      ERROR: { target: 'error' }
  },
  running: {
      PAUSE: { target: 'paused' },
      COMPLETE: { target: 'completed' },
      ERROR: { target: 'error' }
  }
33});

Implementing State Transitions in JavaScript State Machine with Event Handling

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