function Cat(name, color) {
    this.name = name;
    this.color = color;
}
Cat.prototype.type = 'mammal';
Cat.prototype.eat = function() { console.log('eat fish'); };
var cat1 = new Cat('Kitty', 'white');
var cat2 = new Cat('Smokey', 'black');
console.log(cat1.type); // mammal
console.log(cat1.eta === cat2.eta);     // TRUE, same reference
console.log(cat1.constructor === Cat)   // TRUE, from Person.prototype
//javascript/6960