js 多态的实现

function Animal() {}
Animal.prototype.sayName = function() {
    console.log('My name is Animal');
};

function Dog() {}
Dog.prototype = new Animal();
Dog.prototype.constructor = Dog;
Dog.prototype.sayName = function() {
    console.log('My name is Dog');
};

function Cat() {}
Cat.prototype = new Animal();
Cat.prototype.constructor = Cat;
Cat.prototype.sayName = function() {
    console.log('My name is Cat');
};

function sayName(animal) {
    animal.sayName();
}

var dog = new Dog();
var cat = new Cat();

sayName(dog); // My name is Dog
sayName(cat); // My name is Cat

function Animal(name) {
    this.name = name;
}
Animal.prototype.sayName = function() {
    console.log('My name is ' + this.name);
};

function Dog(name) {
    Animal.call(this, name);
}
Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;

function Cat(name) {
    Animal.call(this, name);
}
Cat.prototype = Object.create(Animal.prototype);
Cat.prototype.constructor = Cat;

function sayName(animal) {
    animal.sayName();
}

var dog = new Dog('Buddy');
var cat = new Cat('Whiskers');

sayName(dog); // My name is Buddy
sayName(cat); // My name is Whiskers