js的继承实现方式

　　　　　function Animal(age){
            this.age = age;
            this.say = function(){
                console.log(‘age:‘+this.age);
            };
        }    
        function Dog(age,nickname){
            Animal.call(this,age);
            // Animal.apply(this,[age]);
            this.nickname = nickname;
            this.say = function(){
                console.log(‘nickname:‘+this.nickname+‘,age:‘+this.age);
            };
        }    
        var animal = new Animal(11);
        var dog = new Dog(12,‘dog‘);
        animal.say();
        dog.say();        

　　　　 function Animal(){}
        Animal.prototype.age = 11;
        Animal.prototype.say = function(){
            console.log(‘age:‘+this.age);
        };
        function Dog(){}
        Dog.prototype = new Animal();
        Dog.prototype.nickname = ‘dog‘;
        Dog.prototype.say =    function(){
            console.log(‘nickname:‘+this.nickname+‘,age:‘+this.age);
        }; 
        var animal = new Animal();
        var dog = new Dog();
        animal.say();
        dog.say();

　　　　　function Animal(age){
            this.age = age;
        }    
        Animal.prototype.say = function(){
            console.log(‘age:‘+this.age);
        };
        function Dog(age,nickname){
            Animal.call(this,age);
            // Animal.apply(this,[age]);
            this.nickname = nickname;
        }    
        Dog.prototype.say =    function(){
            console.log(‘nickname:‘+this.nickname+‘,age:‘+this.age);
        }; 
        var animal = new Animal(11);
        var dog = new Dog(12,‘dog‘);
        animal.say();
        dog.say();