Now that we know when and why we would want to use a stack, let's move on to implementing one. As discussed in the preceding section, we will use a WeakMap() for our implementation. You can use any native data type for your implementation, but there are certain reasons why WeakMap() would be a strong contender. WeakMap() retains a weak reference to the keys that it holds. This means that once you are no longer referring to that particular key, it gets garbage-collected along with the value. However, WeakMap() come with its own downsides: keys can only be nonprimitives and are not enumerable, that is, you cannot get a list of all the keys, as they are dependent on the garbage collector. However, in our case, we are more concerned with the values that our WeakMap() holds rather than keys and their internal memory management.