继承的5种实现方式

function SuperClass(){
    this.name = 'jack';
    this.age = 12;
}
SuperClass.prototype.sayhi = function() {
    console.log('hi, i am '+ this.name)
}

function SubClass() {}
SubClass.prototype = new SuperClass();
var obj = new SubClass()

function SuperClass(name, age){
    this.name = name;
    this.age = age;
}
SuperClass.prototype.sayhi = function() {
    console.log('hi, i am '+ this.name)
}
function SubClass(name, age) {
    SuperClass.call(this, name, age) 
}
var obj = new SubClass('ken', 23)

// 组合继承
function SuperClass(name, age){
    this.name = name;
    this.age = age;
}
SuperClass.prototype.sayhi = function() {
    console.log('hi, i am '+ this.name)
}
function SubClass(name, age, sex) {
    SuperClass.call(this, name, age)
    this.sex = sex
}
SubClass.prototype.getName = function() {
    console.log(this.name)
} 
SubClass.prototype = SuperClass.prototype 
// SubClass.prototype = new SuperClass
SubClass.prototype.constructor = SubClass

var obj = new SubClass('ken', 23, 0)

function SuperClass(name, age){
    this.name = name;
    this.age = age;
}
SuperClass.prototype.sayhi = function() {
    console.log('hi, i am '+ this.name)
}
function SubClass(name, age, sex) {
    SuperClass.call(this, name, age)
    this.sex = sex
}
SubClass.prototype = Object.create(SuperClass.prototype,{
    constructor: {
        value: SubClass
    }
})
var obj = new SubClass('ken', 23, 0)

class SuperClass {
    construtor(name, age) {
        this.name = name;
        this.age = age;
    }
    
}
class SubClass extends SuperClass  {
    constructor(name, age, num) {
        super(name, age)
        this.num = num
    }
}
var instance1 = new SubClass("1", 20, 1)

class Super {}
class Sub extends Super {}

const sub = new Sub();

Sub.__proto__ === Super; // true

function Super() {}
function Sub() {}

Sub.prototype = new Super();
Sub.prototype.constructor = Sub;

var sub = new Sub();

Sub.__proto__ === Super.prototype;  // false

Sub.__proto__ === Function.prototype; // true