js 对象的封装，继承，多态的理解

//对象的继承，这里采用构造函数继承+类式继承function Person(name,sex,age){this.name = name;this.sex = sex;this.age = age;}Person.prototype.getName = function(){return this.name;}function Student(school,name,sex,age){Person.call(this,name,sex,age);//构造函数继承，保证实例之间不会互相影响this.school = school;}Student.prototype = new Person();//类式继承，解决构造函数继承不能继承定义在外面的原型链的方法var student1 = new Student("西都小学1","1","男1",21);var student2 = new Student("西都小学2","2","男2",22);console.log(student1.getName());//1student1.name = "修改";console.log(student1.name);//修改console.log(student2.name);//2//多态就是构造函数根据传入的变量不同，对同一方法，有不同的返回结果//比如function Math(){function zero(){return 10;}function one(num){return 10+num;}this.add = function(){switch(arguments.length){case 0:return zero();break;case 1:return one(arguments[0]);break;}}}var math1 = newMath();console.log(math1.add());//10console.log(math1.add(10));//20//封装就是有些私有的属性和方法，用户只能通过公有方法去访问这些私有属性function Company(name){var personNum = 0;this.name = name;this.getNum = function(){return personNum;}this.addNum = function(){personNum++;}}var company1 = new Company("保时捷");var company2 = new Company("宝马");console.log(company1.getNum());//0company1.addNum();console.log(company1.getNum());//1console.log(company2.getNum());//0console.log(company1.personNum);//undefined