Egg timer with Pebble.js

app.js

var UI = require('ui');
var Vector2 = require('vector2');
var Vibe = require('ui/vibe');

var menu = new UI.Menu({
    sections: [{
      title: 'Egg size',
      items: [{
        title: 'Medium',
      }, {
        title: 'Large'
      }, {
        title: 'Extra-large'
      }]
    }]
  });

var mdMenu = new UI.Menu({
    sections: [{
      title: 'Egg timer',
      items: [{
        title: 'Runny',
        subtitle: '3m'
      }, {
        title: 'Soft',
        subtitle: '4m'
      }, {
        title: 'Firm',
        subtitle: '5m'
      }]
    }]
  });

var lgMenu = new UI.Menu({
    sections: [{
      title: 'Egg timer',
      items: [{
        title: 'Runny',
        subtitle: '4m'
      }, {
        title: 'Soft',
        subtitle: '5m'
      }, {
        title: 'Firm',
        subtitle: '6m'
      }]
    }]
  });

var xlMenu = new UI.Menu({
    sections: [{
      title: 'Egg timer',
      items: [{
        title: 'Runny',
        subtitle: '5m'
      }, {
        title: 'Soft',
        subtitle: '6m'
      }, {
        title: 'Firm',
        subtitle: '7m'
      }]
    }]
  });

var timeouts = {
   '3m': 18,
   '4m': 24,
   '5m': 30,
   '6m': 36,
   '7m': 42
};


menu.on('select', function(e) {
    if (e.itemIndex === 0){
      mdMenu.show();
    } else if (e.itemIndex === 1){
      lgMenu.show();
    } else {
      xlMenu.show();
    }
});

mdMenu.on('select', onTimerSelect);
lgMenu.on('select', onTimerSelect);
xlMenu.on('select', onTimerSelect);


var globalIntervalId;

function onTimerSelect(e){
  clearInterval(globalIntervalId);
  var timeout = timeouts[e.item.subtitle];
  
  globalIntervalId = timer(timeout);
}

menu.show();

var readyMessage = new UI.Card({
  title: 'Done',
  body: 'Your eggs are ready!'
});

function timer(timerInSec){
  var intervalId = setInterval(function(){
    timerInSec--;

    if (timerInSec == 1){
      Vibe.vibrate('double');
    }
    if (timerInSec > 0){
      textfield.text(getTimeString(timerInSec));
    } else {
      readyMessage.show();
      wind.hide();

      clearInterval(globalIntervalId);

      Vibe.vibrate('long');
    }
  }, 1000);
  
  var wind = new UI.Window();
  var textfield = new UI.Text({
    position: new Vector2(0, 50),
    size: new Vector2(144, 30),
    font: 'bitham-42-light',
    text: getTimeString(timerInSec),
    textAlign: 'center'
  });

  wind.add(textfield);
  wind.show();
  wind.on('hide', function(){
    clearInterval(globalIntervalId);
  });
  return intervalId;
}

function getTimeString(timeInSec){
  var minutes = parseInt(timeInSec / 60);
  var seconds = timeInSec % 60;
  return minutes + ':' + (seconds < 10 ? ('0' + seconds) : seconds);
}