原型指向改变如何如何添加方法和访问
function Person(age) {
this.age = age;
}
Person.prototype.eat = function () {
console.log("eat")
}
function Student(sex) {
this.sex = sex
}
Student.prototype.sayHi = function () {
console.log("nihao")
}
Student.prototype = new Person(10);