class Person{ 
    constructor(name){ 
      let _num = 100; 

      this.name = name;
      this.getNum = function(){
        return _num;
      } 
      this.addNum = function(){
        return ++_num
      } 
    }
  }
  
  const tom = new Person('tom')
  const jack = new Person('jack')
  tom.addNum() 
  console.log(tom.getNum()) //101
  console.log(jack.getNum()) //100 

const Person = (function () {
    let _num = 100;

    return class _Person {
      constructor(name) {
        this.name = name; 
      }
      addNum() {
       return ++_num
      }
      getNum() {
       return _num
      } 
    }
  })() 

  const tom = new Person('tom')
  const jack = new Person('jack') 
  tom.addNum()
  console.log(tom.getNum()) //101
  console.log(jack.getNum()) //101 

const name = Symbol('名字')
const person = { // 类名
  [name]:'www',
  say(){
    console.log(`name is ${this[name]} `) 
  } 
} 
person.say()
console.log(name)

const Person = (function () {
 let _num = Symbol('_num：私有变量');
 
 return class _Person {
  constructor(name) {
   this.name = name;
   this[_num] = 100
  }
  addNum() {
   return ++this[_num]
  }
  getNum() {
   return this[_num]
  } 
 }
})()

const tom = new Person('tom')
const jack = new Person('jack')

console.log(tom.addNum()) //101 
console.log(jack.getNum()) //100

const Parent = (function () {
 const privates = new WeakMap();

 return class Parent {
  constructor() {
   const me = {
    data: "Private data goes here"
   };
   privates.set(this, me);
  }
  getP() {
   const me = privates.get(this);
   return me
  }
 } 
})()

let p = new Parent()
console.log(p)
console.log(p.getP())