Symbol

symbol.js

// demo
let privateDataStore = {
	set(val){
    	let key = Symbol(Math.random().toString(32).substr(2))
        this[key]=val
        return key
    }
    get(key){
    	return this[key]
    }
}

//use
let key = privateDataStore('hello')
privateDataStore[key]
privateDataStore.get(key)