Class

推薦使用的ES6語法糖，英文意思可以理解成類別、模板，也是JavaScript的prototype語法的概念，和construector function一樣可以製作很多個物件，且不需要特別設定prototype。

用class改寫前：

//函數建構式 
function Person(name, age, height,weight) { 
    this.name = name, 
    this.age = age, 
    this.height = height 
    this.weight = weight  
} 
//做Prototype的function 
Person.prototype.sayHi= function() { 
    console.log(this.name + " says hi."); 
} 
Person.prototype.intro= function() {  
    console.log("hi my name is " + this.name + ".");  
}
let Harry = new Person("Harry",24,160,60);
let Wilson = new Person("Wilson Ren",25,179,79);
console.log(Harry);
Harry.sayHi();

class改寫後：

class Person2 {
    //constructor function
    constructor(name,age,height,weight) {
        this.name = name, 
        this.age = age, 
        this.height = height 
        this.weight = weight
    }
    sayHi() {
        console.log(this.name + " says hi.");
    }
    intro() {
        console.log("hi my name is " + this.name + ".");
    }
}
let Harry2 = new Person2("Harry2",24,160,60); 
let Wilson2 = new Person2("Wilson2 Ren",25,179,79);
console.log(Harry2);
Harry2.sayHi();

//檢查以上2個新物件使用的方法是否相同 
console.log(Wilson2.sayHi === Harry2.sayHi);

改寫前、後的執行結果：它們使用的sayHi()是相同的所以是true，且不需要特別設定prototype

原型繼承使用Object.create()

Object.create()方法：
創建一個新物件，把現有物件當作新建物件的原型使用，讓新建物件繼承現有物件的methods。
語法：

Object.create(proto) 
Object.create(proto, propertiesObject)

把Person當原型，讓Student繼承Person的方法，例：

//函數建構式
function Person(name, age, height,weight) {
    this.name = name,
    this.age = age,
    this.height = height
    this.weight = weight
}
Person.prototype.sayHi= function() {
    console.log(this.name + " says hi."); 
}
Person.prototype.intro= function() { 
    console.log("hi my name is " + this.name + "."); 
}

//Student
function Student(name, age, height,weight,major,grade) {
    //這裡的this指向Student
    Person.call(this, name, age, height,weight);
    this.major = major,
    this.grade= grade
}
//讓Student的原型，繼承Person的原型
Student.prototype = Object.creat(Person.prototype);

let Harry = new Student("Harry",24,160,60,"CS",3.85);
console.log(Harry);
Harry.sayHi();

執行結果：可以看到Student繼承了Person的方法。

當然Student也可建立自己獨有的Student.prototype方法。

extends(類別繼承)

Class(類別) 可用 extends(擴展、繼承)語法繼承，使用extends可以繼承另一個類別的屬性(properties)與方法(method)。
extends關鍵字可用於建立一個自訂類別或內建類別的子類別。
它繼承的原型 .prototype 必須是 Object 或 null。
語法：

class ChildClass extends ParentClass { ... }

用class改寫和extends，改寫Object.create()

原本使用Object.create 與 原型繼承，用class改寫後：

class Person2 {
    //constructor function
    constructor(name,age,height,weight) {
        this.name = name, 
        this.age = age, 
        this.height = height 
        this.weight = weight
    }
    sayHi() {
        console.log(this.name + " says hi.");
    }
    intro() {
        console.log("hi my name is " + this.name + ".");
    }
}



//從這裡開始改寫
//Student2是Person2母集合裡的子集合
class Student2 extends Person2 {
    constructor(name, age, height,weight,major,grade){
        super(name,age,height,weight); //super有代表母集合的意思
        this.major = major,
        this.grade= grade
    }
    study() {
        console.log("I'm studying now.");
    }
} 
let Harry2 = new Student2("Harry2",24,160,60,"CS",3.85);
console.log(Harry2);

//可使用Person的方法
Harry2.sayHi();
Harry2.study();

執行結果：可以看見Student2繼承了Person2的方法

參考資料：

extends - JavaScript | MDN
[JS]類別(class) - constructor、extends、super、static、Getter & Setter - HackMD
Object.create() - JavaScript | MDN
JavaScript 核心篇 學習筆記: Chap.56/57–使用 Object.create 建立多層繼承 | by Yi-Ning | Medium