JavaScript 继承

JavaScript 继承

• 原型链继承

// An highlighted block
<script>
	function Animal(name, sex) {
        this.name = name || "动物";
        this.sex = sex || "性别";
        this.sleep = function () {
            return this.name + "睡觉";
        }
    }
     Cat.prototype=new Animal();
     Cat.prototype.eat=function (){
     return this.name+"吃饭";
     }
     Cat.prototype.name="小猫";
     Cat.prototype.sex="公";
     var cat=new Cat();
     console.log(cat.name);
     Mouse.prototype=new Animal();
     Mouse.prototype.name="乔治";
     Mouse.prototype.sex="公";
     var mouse=new Mouse();
     var mouse1=new Mouse();
     console.log(mouse.name);
     console.log(mouse1.name);
     //子类的实例 即是自身 也是父类
     console.log(cat instanceof Cat);
     console.log(cat instanceof Animal);
     console.log(cat);
</script>

注释：prototype 属性共享，给子类原型追加方法或者属性必须在原型继承之后；原型继承不能进行多继承

• 构造继承

// An highlighted block
<script>
	function Animal(name, sex) {
        this.name = name || "动物";
        this.sex = sex || "性别";
        this.sleep = function () {
            return this.name + "睡觉";
        }
    }
     function AnimalType(type){
     	this.type=type || "类别";
     }
     function Cat(name,sex,type){
     	Animal.call(this,name,sex);
     	AnimalType.apply(this,[type]);
     		this.eat=function (){
     		return this.name+"爱吃老鼠";
     	}
     }
     function Mouse(name,sex,type){
     	Animal.call(this,name,sex);
     	AnimalType.apply(this,[type]);
     	this.eat=function (){
     		return this.name+"爱偷大米";
     	}
     }
     var cat=new Cat("小花","公","猫科");
     var cat1=new Cat("小黑","母","猫科");
     console.log(cat.eat());
     console.log(cat1.eat());
     console.log(cat instanceof Animal);
     console.log(cat);
     var mouse=new Mouse("小小","公","鼠科");
     console.log(mouse);
</script>

注释：

• 对象里面的this替换 参数的区别 1.替换的对象 2.参数列表 call(this,1,2,3,4,5) apply(this,[1,2,3,4,5,6])
• 在创建子类的实例的时候可以向父类传参，它可以实现多继承，子类的实例只能是自身
• 组合继承

// An highlighted block
<script>
//例一
	function Animal(name, sex) {
        this.name = name || "动物";
        this.sex = sex || "性别";
        this.sleep = function () {
            return this.name + "睡觉";
        }
    }
    function AnimalType(type) {
     	this.type = type || "类别";
    }
    function Cat(type) {
     	AnimalType.call(this, type);
    }
    Cat.prototype = new Animal();
    Cat.prototype.name = "小花";
    function Mouse() {

     }
     var cat = new Cat("猫科");
     console.log(cat);
     console.log(cat instanceof  Animal);
     console.log(cat);
//例二
     function Grade(score) {
     	this.score = score || "0";
     }
     function Person(name, sex) {
     	this.name = name || "人";
     	this.sex = sex || "默认";
     }
     function Job(job) {
     	this.job = job || "闲人"
     }
     function Children(name, sex, job, score) {
     	Person.apply(this, [name, sex]);
     	Job.call(this, job);
     	Grade.call(this, score);
     }
     var s = new Children("小强", "男", "学生", 485);
     var s1 = new Children("小花", "女", "学生", 657);
     console.log(s);
     console.log(s1);*/
    
</script>

注释：原型+构造继承可以实现多继承，有数据可以共享；子类的实例即是自身，也是父类

• 实例继承

// An highlighted block
<script>
	function Animal(name, sex) {
        this.name = name || "动物";
        this.sex = sex || "性别";
        this.sleep = function () {
            return this.name + "睡觉";
        }
    }
    function Cat(name, sex) {
     	this.eat=function (){

    }
    var animale = new Animal(name, sex);
     	return animale;
    }
    function Mouse() {

    }
    var cat=new Cat("小猫","公");
    console.log(cat);
    var cat1=Cat("小花","母");
    console.log(cat1);
    console.log(cat instanceof Cat);
    console.log(cat instanceof Animal);
</script>

注释：不限制调用方式，子类的实例不是本身，而是父类

• 组合寄生继承

// An highlighted block
<script>
	function Super(b){
     	this.b = b;
     	this.fun = function(){}
     }
     Super.prototype.c = function(){console.log(1111)}
     Super.prototype.name="张三";
     function f1(){

     }
     var f = new f1();
     //f.c= Super.prototype.c;
     f.prototype= Super.prototype;
     //f1.prototype=Super.prototype;
     function Foo(a,b){
     	this.a = a;
     	Super.call(this,b);
     }
     Foo.prototype =f;
     var foo1 = new Foo(1,2);
     console.log(foo1.prototype.c());
</script>

注释：继承时有些模式，拿不到父类的原型方法和属性，考虑寄生模式