Two ways to declare private variables in JavaScript

function outside(){
	let val = 123;
	function inside(){
		return val;
	}
	return inside;
}
console.log(outside()());//123

//The same can be accessed, but not modified, achieving the effect of the above code const val = 123;
console.log(val);//123

function person(){ 
 let _name = 'unknown';
 let _age = 18;
 let _sex = 'man';

 function setName(name){
  _name = name || 'unknown';
 }

 function getName(){
  return _name;
 }

 function setAge(age){
  if(typeof age === 'number'){
   _age = Math.floor(age);
  }else{
   throw Error("typeof age !== 'number'");
  }
 }

 function getAge(){
  return _age;
 }

 function setSex(sex){
  if(sex === 'man' || sex === 1){
   _sex = 'man';
  }else if(sex === 'woman' || sex === 0){
   _sex = 'woman';
  }else{
   throw Error('input error');
  }
 }

 function getSex(){
  return _sex;
 }

 return {
  setName : setName,
  getName : getName,
  setAge : setAge,
  getAge : getAge,
  setSex : setSex,
  getSex : getSex
 }
}

let xiaoming = person();
let xiaohong = person();
xiaoming.setName('xiaoming');
xiaohong.setName('xiaohong');
console.log('xiaoming name : ' + xiaoming.getName());//xiaoming name : xiaoming
console.log('xiaohong name : ' + xiaohong.getName());//xiaohong name : xiaohong

xiaoming.setAge(19.3333);
xiaohong.setAge('16');//Uncaught Error: typeof age !== 'number'
console.log('xiaoming age : ' + xiaoming.getAge());//xiaoming age : 19
console.log('xiaohong age : ' + xiaohong.getAge());//xiaohong age : 18


xiaoming.setSex(1);
xiaohong.setSex('woman');
console.log('xiaoming sex : ' + xiaoming.getSex());//xiaoming sex : man
console.log('xiaohong sex : ' + xiaohong.getSex());//xiaohong sex : woman

let nameWeakMap = new WeakMap();
let ageWeakMap = new WeakMap();
let sexWeakMap = new WeakMap();

function person(){
 let _hash = Object.create(null);
 nameWeakMap.set(_hash,'unknown');
 ageWeakMap.set(_hash,18);
 sexWeakMap.set(_hash,'man');
 function setName(name){
  nameWeakMap.set(_hash,name || 'unknown');
 }

 function getName(){
  return nameWeakMap.get(_hash);
 }

 function setAge(age){
  if(typeof age === 'number'){
   ageWeakMap.set(_hash,Math.floor(age));
  }else{
   throw Error("typeof age !== 'number'");
  }
 }

 function getAge(){
  return ageWeakMap.get(_hash);
 }

 function setSex(sex){
  if(sex === 'man' || sex === 1){
   sexWeakMap.set(_hash,'man');
  }else if(sex === 'woman' || sex === 0){
   sexWeakMap.set(_hash,'woman');
  }else{
   throw Error('input error');
  }
 }

 function getSex(){
  return sexWeakMap.get(_hash);
 }

 return {
  setName : setName,
  getName : getName,
  setAge : setAge,
  getAge : getAge,
  setSex : setSex,
  getSex : getSex
 }
}

let xiaoming = person();
let xiaohong = person();
xiaoming.setName('xiaoming');
xiaohong.setName('xiaohong');
console.log('xiaoming name : ' + xiaoming.getName());//xiaoming name : xiaoming
console.log('xiaohong name : ' + xiaohong.getName());//xiaohong name : xiaohong

xiaoming.setAge(19.3333);
xiaohong.setAge('16');//Uncaught Error: typeof age !== 'number'
console.log('xiaoming age : ' + xiaoming.getAge());//xiaoming age : 19
console.log('xiaohong age : ' + xiaohong.getAge());//xiaohong age : 18


xiaoming.setSex(1);
xiaohong.setSex('woman');
console.log('xiaoming sex : ' + xiaoming.getSex());//xiaoming sex : man
console.log('xiaohong sex : ' + xiaohong.getSex());//xiaohong sex : woman