//ES6 Maps and Sets - The WeakMap

let cardAce = {
  name : 'Ace of Spades'
};

let cardKing = {
  name : 'King of Clubs'
};


// In WeakMap's your key has to be a javascript object
// weakmaps hold 'weak' references meaning it is garbage collected
// therefore keys must be referencesTypes 
// weakmaps identify which objects arent being used anymore and removes them from memory
// looping is not possible, but you can get an object with a key

let keyOne = {a:1};
let keyTwo = {b:2};


let deck = new WeakMap();  
deck.set(keyOne, cardAce);  
deck.set(keyTwo, cardKing); 

// Get object from weakmap by key
console.log(deck.get(keyOne))