Javascriptのプロトタイプの例

var Car = function (color, price){
  this.distanceCovered = 0;
  this.color = color;
  this.price = price;
  this.gazorin = 0;
  return this;
}

Car.prototype.addGazorin = function (l){
  this.gazorin += l;
  return this;
}

Car.prototype.run = function (){
  var distance = 0;
  if (this.gazorin > 0){
    while (this.gazorin){
      this.distanceCovered ++;
      distance ++;
      this.gazorin --;
    }
  }
  return distance;
}

var car = new Car("red", 1000000).addGazorin(100);

var distance = car.run();
// 100