class Creator {
  create(name) {
    return new Product(name);
  }
}
let creator = new Creator();
let p = creator.create("p");

class SingleObject {
  login() {
    console.log("login...");
  }
}
SingleObject.getInstance = (function() {
  let instance;
  return function() {
    if (!instance) {
      instance = new SingleObject();
    }
    return instance;
  };
})();
let obj1 = SingleObject.getInstance();
obj1.login();

class Adaptee {
  specificRequest() {
    return "德国标准";
  }
}
class Target {
  constructor() {
    this.adaptee = new Adaptee();
  }
  request() {
    let info = this.adaptee.specificRequest();
    return `${info}--转换--中国标准`;
  }
}
let target = new Target();
target.request();

function log(target, name, descriptor) {
  var oldValue = descriptor.value;
  descriptor.value = function() {
    console.log(`Calling ${name} with`, arguments);
    return oldValue.apply(this, arguments);
  };
  return descriptor;
}
class Math {
  @log
  add(a, b) {
    return a + b;
  }
}
const math = new Math();
math.add(2, 4);

@decorator
class A {}
//等同于
class A {}
A = decorator(A) || A;

let star = {
  name: "张XX",                    // 明星
  age: 25,
  phone: "13800138000"
};
let agent = new Proxy(star, {     // 经纪人
  get: function(target, key) {
    if (key === "phone") {        // 返回经纪人自己的手机号
      return "18012345678";
    }
    if (key === "price") {        // 明星不报价，经纪人报价
      return 120000;
    }
    return target[key];
  },
  set: function(target, key, val) {
    if (key === "customPrice") {
      if (val < 100000) {
        throw new Error("价格太低");
      } else {
        target[key] = val;
        return true;
      }
    }
  }
});

function bindEvent(elem, type, selector, fn) {
  if (fn == null) {
    fn = selector;
    selector = null;
  }
  //...
}
//调用可以有两种
bindEvent(elem, "click", "#div", fn);
bindEvent(elem, "click", fn);

class Subject {                      // 主题，接收状态变化，触发每个观察者
  constructor() {
    this.state = 0;
    this.observers = [];
  }
  getState() {                       //获取状态
    return this.state;
  }
  setState(state) {                  //修改状态
    this.state = state;
    this.notifyAllObservers();
  }
  attach(observer) {                 //添加观察者
    this.observers.push(observer);
  }
  notifyAllObservers() {             //通知所有观察者
    this.observers.forEach(observer => {
      observer.update();
    });
  }
}
class Observer {                     // 观察者，等待被触发
  constructor(name, subject) {
    this.name = name;
    this.subject = subject;
    this.subject.attach(this);
  }
  update() {
    console.log(`${this.name} update, state: ${this.subject.getState()}`);
  }
}
let s = new Subject();
let o1 = new Observer("o1", s);
let o2 = new Observer("o2", s);
s.setState(1);
s.setState(2);

class Iterator {
  constructor(conatiner) {
    this.list = conatiner.list;
    this.index = 0;
  }
  next() {
    if (this.hasNext()) {
      return this.list[this.index++];
    }
    return null;
  }
  hasNext() {
    if (this.index >= this.list.length) {
      return false;
    }
    return true;
  }
}
class Container {
  constructor(list) {
    this.list = list;
  }
  getIterator() {
    return new Iterator(this);
  }
}
let container = new Container([1, 2, 3, 4, 5]);
let iterator = container.getIterator();
while (iterator.hasNext()) {
  console.log(iterator.next());
}

var fsm = new StateMachine({
  init: "solid",
  transitions: [
    { name: "melt", from: "solid", to: "liquid" },
    { name: "freeze", from: "liquid", to: "solid" },
    { name: "vaporize", from: "liquid", to: "gas" },
    { name: "condense", from: "gas", to: "liquid" }
  ],
  methods: {
    onMelt: function() { console.log("I melted"); },
    onFreeze: function() { console.log("I froze"); },
    onVaporize: function() { console.log("I vaporized"); },
    onCondense: function() { console.log("I condensed"); }
  }
});

const person = {
  isHuman: false,
  printIntroduction: function () {
    console.log(`My name is ${this.name}`);
  }
};
const me = Object.create(person);
me.name = "Matthew";
me.isHuman = true;

{
  tag: "div",
  attr: {
    className: "container"
  },
  children: [
    {
      tag: "p",
      attr: {},
      children: ["123"]
    },
    {
      tag: "p",
      attr: {},
      children: ["456"]
    }
  ]
}

class User {
  constructor(type) {
    this.type = type;
  }
  buy() {
    if (this.type == "ordinary") {
      console.log("普通用户购买");
    } else if (this.type == "member") {
      console.log("会员用户购买");
    } else if (this.type == "vip") {
      console.log("VIP用户购买");
    }
  }
}
//策略模式生成三个类，各自实现buy()方法
class UserOrdinary {
  buy() {
    console.log("普通用户购买");
  }
}
class UserMember {
  buy() {
    console.log("会员用户购买");
  }
}
class UserVip {
  buy() {
    console.log("VIP用户购买");
  }
}

class Action {
  handle() {
    handle1();
    handle2();
    handle3();
  }
  handle1() { }
  handle2() { }
  handle3() { }
}

class Action {
  constructor(name) {
    this.name = name;
    this.nextAction = null;
  }
  setNextAction(action) {
    this.nextAction = action;
  }
  handle() {
    console.log(`${this.name} 审批`);
    if (this.nextAction != null) {
      this.nextAction.handle();
    }
  }
}
let a1 = new Action("组长");
let a2 = new Action("经理");
let a3 = new Action("总监");
a1.setNextAction(a2);
a2.setNextAction(a3);
a1.handle();

class Receiver {
  exec() {
    console.log("执行");
  }
}
class Command {
  constructor(receiver) {
    this.receiver = receiver;
  }
  cmd() {
    console.log("触发命令");
    this.receiver.exec();
  }
}
class Invoker {
  constructor(command) {
    this.command = command;
  }
  invoke() {
    console.log("开始");
    this.command.cmd();
  }
}
let solider = new Receiver();             //士兵
let trumpeter = new Command(solider);     //小号手
let general = new Invoker(trumpeter);     //将军
general.invoke();

document.execCommand("bold");
document.execCommand("undo");

class Mediator {        //中介者
  constructor(a, b) {
    this.a = a;
    this.b = b;
  }
  setA() {
    let number = this.b.number;
    this.a.setNumber(number * 100);
  }
  setB() {
    let number = this.a.number;
    this.b.setNumber(number / 100);
  }
}
class A {
  constructor() {
    this.number = 0;
  }
  setNumber(num, m) {
    this.number = num;
    if (m) {
      m.setB();         //通过中介者修改
    }
  }
}
class B {
  constructor() {
    this.number = 0;
  }
  setNumber(num, m) {
    this.number = num;
    if (m) {
      m.setA();         //通过中介者修改
    }
  }
}