weakmap-example.js

function createStorage() {
  var
    _,
    map
  ;

  map = new WeakMap();

  return (function (object) {
    var
      store
    ;

    if (! store) {
      map.set(object, (store = Object.create(null)))
    }

    return store;
  });

  _ = createStorage();

  function Player() {
    _(this).lifeCount = 3;
  }
}