继承

class User{
            constructor(name,pwd){
                this.name=name
                this.pwd=pwd
            }

            showName(){
                alert(this.name)
            }

            showPwd(){
                alert(this.pwd)
            }
        }

        var user=new User('LiLei',1233)
        user.showName()
        user.showPwd()

        class VipUser extends User{
            constructor(name,pwd,level){
                super(name,pwd)

                this.level=level
            }

            showLevel(){
                alert(this.level)
            }
        }

        var vip=new VipUser('HanMeiMei',23344,4)
        vip.showLevel()

静态方法/属性

const users=[];//该数组将作为User的users属性的初始值

class User{
    constructor(firstname,lastname,age){
        this.firstname=firstname,
        this.lastname=lastname,
        this.age=age
    }

    getName()
    {
        return `${this.firstname} ${this.lastname}`
    }
    
    static insert(firstname,lastname,age)
    {
        const u=new User(firstname,lastname,age)
        User.users.push(u)
        return u
    }

    static getOnebyfirstname(firstname)
    {
        return Users.find(u=>u.firstname===firstname)
    }

    //定义静态方法
    static list(query){
        return User.users
    }

    //定义静态属性 等效于 static users=users，只是这种写法js暂不支持
    static get ['users'](){
        return users
    }
}

等效于

class User{
    constructor(firstname,lastname,age){
        this.firstname=firstname,
        this.lastname=lastname,
        this.age=age
    }

    getName()
    {
        return `${this.firstname} ${this.lastname}`
    }
    
    static insert(firstname,lastname,age)
    {
        const u=new User(firstname,lastname,age)
        User.users.push(u)
        return u
    }

    static getOnebyfirstname(firstname)
    {
        return Users.find(u=>u.firstname===firstname)
    }

    static list(query){
        return User.users
    }
}
User.users=[];