Stefan Weiss wrote:
> I was talking about reference types with a co-worker a couple of months
> ago, and we found an analogy that seemed to help:

> One can imagine variables as small envelopes, just large enough to hold
> a single piece of paper. Some things can fit on this piece of paper
> entirely, like numbers and strings, others are too large, like objects.

> When you create an object, it's like handing your cloak (the object) to
> a checkroom attendant. He will put the cloak on a rack and hand you a
> paper receipt to identify it later. You put this piece of paper in your
> envelope: your variable now contains a reference to an object.

> Now you can use this receipt to access your cloak anytime. You can copy
> the receipt to another envelope and it will still work. You can show it
> to other attendants (methods), who will copy it from you and can now
> also access your cloak.

> When you empty your envelope, you lose the reference. The cloak still
> exists, but you won't be able to find it again. After a while, the
> checkroom attendant may (or may not) notice that this cloak has been
> hanging around for weeks, and will throw it away (objects with a
> reference count of zero may be garbage collected).

> The analogy is getting a little stretched now, but bear with me...

> When you write options.add(o), that's like showing your receipt to an
> attendant and saying "take this cloak from wherever it is and hang it on
> the tree outside" (the DOM tree). You can do that any number of times,
> but in the end your cloak will be hanging on the tree only once. If you
> put something else in your envelope, like a blank piece of paper (o =
> null), the cloak on the tree is unaffected by this. You just don't have
> an easy way to find it again.