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machine.js

// DEMO: Side effects with activities
// Look for beebing in the console
const initial = "idle";

const states = {
  idle: {
    on: {
      ALARM: "alarming"
    }
  },
  alarming: {
    on: {
      STOP: "idle"
    },
    activities: ["beeping"]
  }
};

const config = {
  id: "alarmClock",
  initial,
  states
};

const options = {
  activities: {
    beeping: (context, event) => {
      const beep = () => {
        console.log("beep");
      };
      beep();
      const intervalId = setInterval(beep, 1000);
      return () => clearInterval(intervalId);
    }
  }
};

const machine = Machine(config, options);