class StateMachine {
  constructor() {
    this.state = 'idle';
    this.transitions = {
      idle: { start: 'running' },
      running: { pause: 'paused', stop: 'idle' },
      paused: { resume: 'running', stop: 'idle' }
    };
  }
  
  transition(action) {
    const validTransitions = this.transitions[this.state];
    if (validTransitions && validTransitions[action]) {
      this.state = validTransitions[action];
      return true;
    }
    return false;
  }
}

const machine = new StateMachine();
console.log(machine.transition('pause'));
console.log(machine.state);
console.log(machine.transition('start'));
console.log(machine.state);