js原型继承--使用构造函数和空函数修复原型链解决的问题
//父类构造函数
function People(props){
this.name = props.name;
this.speak = function (){
alert(this.name + ' is speaking');
}
}
//子类构造函数
function Teacher(props){
People.call(this,props);
this.teach = function(){
alert(this.name+' is teaching');
}
this.speak = function (){
alert('when '+this.name+'is speaking, he is teaching')
}
}
//空函数用来修复原型链
function Adapter(){}
Adapter.prototype = People.prototype;
Teacher.prototype = new Adapter();
//修复constructor
Teacher.prototype.constructor = Teacher;
People.prototype.gender = 'male';
//Teacher.prototype.gender = 'female';
var teacher = new Teacher({name:'jack'});
var people = new People({name:'jim'});
teacher.speak();
teacher.teach();
alert(people.gender);
alert(teacher.gender);//如果不修复原型链则teacher的原型链关系:__proto__-->Teacher.prototype-->Object.prototype-->null
//则People.prototype扩展属性的时候无法继承到
//如果直接Teacher.prototype=People.prototype, 则会引用同一个prototype, 给Teacher.prototype扩展属性的时候会影响到People的实例对象
总结就是：
- 每个对象都有一个proto属性
- 每个函数都有一个prototype属性
- 定义一个函数隐含的有
- js访问一个对象的属性或方法的时候会首先在这个对象里面寻找，如果找不到则去原型链指针prototype指向的对象去找，如果找不到会一直沿着prototype找下去
- 一个对象的prototype正常应该指向继承对象
