核心就是：Person.call(this)

例子：
/**
 * 实现 `Student` 构造函数，接受 `name`, `grade` 参数，并且通过借用构造函数继承 `Person`，`Student` 创建的实例满足下列条件：
 * 1. 具有 `name` 和 `grade` 实例属性，分别等于输入的参数。
 * 2. 具有 `selfIntroduce` 原型方法，调用会输出(`console.log`)字符串 `My name is ${name}. I am Grade ${grade}`, 其中 `name` 和 `grade` 分别对应相应的属性值，
 * 3. `student instanceof Student`结果是 `true`, `student instanceof Person` 结果是 `false`。;
 */

/**
 * 实现 `Student` 构造函数，接受 `name`, `grade` 参数，并且通过借用构造函数继承 `Person`，`Student` 创建的实例满足下列条件：
 * 1. 具有 `name` 和 `grade` 实例属性，分别等于输入的参数。
 * 2. 具有 `selfIntroduce` 原型方法，调用会输出(`console.log`)字符串 `My name is ${name}. I am Grade ${grade}`, 其中 `name` 和 `grade` 分别对应相应的属性值，
 * 3. `student instanceof Student`结果是 `true`, `student instanceof Person` 结果是 `false`。;
 */

/**
 * Person 构造函数
 */
function Person(name,grade) {
    this.name = name;
    this.grade = grade;
}
Person.prototype.sayHello = function() {
    console.log('Hi! I am ' + this.name);
}

// TODOS: 实现 Student
function Student(name,grade){
    Person.call(this,name,grade);
   // this.grade = grade;
}
Student.prototype.selfIntroduce = function(){
    console.log("My name is " + this.name + ". I am Grade " + this.grade);
} 

第二种方法：转载自：https://ke.qq.com/classroom/index.html#course_id=233919&term_id=100275850&ch_id=376058&vch_id=46&section_id=168&task_id=1468045591810495
function Person(name) {
    this.name = name;
}
Person.prototype.sayHello = function() {
    console.log('Hi! I am ' + this.name);
}

function Student(name, grade) {
    Person.call(this, name);
    this.grade = grade;
}

Student.prototype.selfIntroduce = function() {
    console.log('My name is ' + this.name + '. I am Grade ' + this.grade);
}

新增的实现继承的方法：

//继承的方法
    function Teacher(name){
        this.name = name;
    }
    Teacher.prototype.sayName = function(){
        return "yuanxing";
    }
    function Student(){
        Teacher.call(this,name);
    }
    Student.prototype = new Teacher();  //实现继承的本质是通过实例父函数，然后赋值给子函数的prototype
    var student = new Student("xiao");
    console.log(student.name)  //xiao
    console.log(student.sayName())  //yuanxing

  方法二：es6中的extends方法
    class Teacher{
        constructor(name,age){
            this.name = name;
            this.age = age;
        }
        sayName(){
            return `父类:${this.name}sd`;
        }
    }
    class Student extends Teacher {
        constructor(name,age,color){
            super(name,age);
            this.color = color;
        }
        checkPhone(){
            return ` ${this.color} `;
        }

    }
    const [age,...rest] = ["xiao","22","red"];  //扩展运算符和结构赋值的结合
    console.log(rest);  //["22","red"]
    let student = new Student("xiao","22","red");
    console.log(student.name);  //xiao
    console.log(student.color); //red
    console.log(student.sayName());  //父类：xiaosd
    console.log(student.checkPhone());  //red