通过一行语句实现继承，ES就是这么强大

1.父类，人类

    function People(name, age, sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    People.prototype.sayHello = function() {
        console.log('你好，我是' + this.name + `我今年${this.age}岁了`);
    };
    People.prototype.sleep = function() {
        console.log(this.name + '开始睡觉，zzzzzz');
    };

2.子类，学生类

    function Student(name, age, sex, scholl, studentNumber) {
        this.name = name;
        this.age = age;
        this.sex = sex;
        this.scholl = scholl;
        this.studentNumber = studentNumber;
    }

  一行语句实现继承：子类的protoype指向新的new出来的父类的实例

Student.prototype = new People();
        Student.prototype.study = function() {
            console.log(this.name + '正在学习');
        }
        Student.prototype.exam = function() {
            console.log(this.name + '正在考试');
        }

3.实例化

    var xiexiaobai = new Student('谢小白', 9, '女', '新兴中学', 259011)

4.xiexiaobai 实例化后的子类能调用父类方法

    xiexiaobai.study();  //谢小白正在学习
    xiexiaobai.exam();   //谢小白正在考试
    xiexiaobai.sayHello();  //你好，我是谢小白我今年9岁了
    xiexiaobai.sleep(); //谢小白开始睡觉，zzzzzz