coffee.js

class Coffee {
  
  constructor() {
    this.refill()
  }
  
  get empty() {
    return this.level === 0;
  }
  
  refill() {
    console.log('fresh pots!')
    this.level = 100;
  }
  
  drink() {
    Math.random() > 0.1 ? console.log('gulp, gulp, gulp') : console.log('hickup..')
    this.level = 0
  }
  
}

var coffee = new Coffee()

setInterval(function() {
  if (coffee.empty) {
    coffee.refill()
  } else {
    coffee.drink()
  }
}, 1000)