var animal=function(name){ //构造函数
  this.name=name;
  this.sayhello=function(){
  alert("hi我是"+this.name);
  };
}
animal.prototype.shout=function(){ //prototype主要作用:给类增加一个新的属性或函数
  alert(this.name+"正在叫！");
};
animal.prototype.game=function(){
  alert(this.name+"正在玩耍！");
};
var dog=new animal("小黑");  //实例化
dog.sayhello();
dog.shout();
dog.game();

var animal=function(name){
  this.name=name;
  this.sayhello=function(){
  alert("hi我是"+this.name);
  };
}
animal.prototype.shout=function(){
  alert(this.name+"正在叫！");
};
animal.prototype.game=function(){
  alert(this.name+"正在玩耍！");
};
var Dog=function(name){
  this.name=name;
  this.shout=function(){   //重写父类的函数
  alert(this.name+"汪汪叫！");
  }
}
Dog.prototype=Cat.prototype=new animal();
var dog=new Dog("小黑");
dog.sayhello();
dog.shout();
dog.game();
var cat=new Cat("小白");
cat.sayhello();
cat.shout();
cat.game();

var animal=function(name){
  this.name=name;
  this.sayhello=function(){
  alert("hi我是"+this.name);
  };
}
Function.prototype.extends=function(superclass){      //extends是保留关键字，不能拿出来单独使用，如var extends=function(){}，而这里可以使用是因为他做为函数的属性添加上去
  this.prototype=new superclass();
};
animal.prototype.shout=function(){
  alert(this.name+"正在叫！");
};
animal.prototype.game=function(){
  alert(this.name+"正在玩耍！");
};
var Dog=function(name){
  this.name=name;
  this.shout=function(){
  alert(this.name+"汪汪叫！");
  }
}
Dog.extends(animal);
var dog=new Dog("小黑");
dog.sayhello();
dog.shout();
dog.game();
var dog=new Dog("小白");
dog.sayhello();
dog.shout();
dog.game();

var animal=function(name){
  this.name=name;
  this.sayhello=function(){
  alert("hi我是"+this.name);
  };
}
animal.prototype.shout=function(){
  alert(this.name+"正在叫！");
};
animal.prototype.game=function(){
  alert(this.name+"正在玩耍！");
};
var Dog=function(name){
  animal.call(this,name);
}
var dog=new Dog("小黑");
dog.sayhello();
dog.shout();
dog.game();