Javascript #prototype

function Animal(type, name, sound) {
  this.type = type;
  this.name = name;
  this.sound = sound;
}

const dog = new Animal("개", "멍멍이", "멍멍");
const cat = new Animal("고양이", "야옹이", "야옹");

Animal.prototype.say = function() {
  console.log(this.sound);
};

dog.say();
cat.say();