var myMap = new WeakMap();
var johnSmith = {name: "Jan", surname: "Kowalski"};
var marioRossi = {name: "Mario", surname: "Rossi"};


myMap.set(johnSmith, "To jest Jan"); 
myMap.set(marioRossi, "To jest Mario"); 

console.log(myMap.get(marioRossi));