section DOM section
Extensions to DOM elements, plus other utilities for DOM traversal and modification.
Prototype's DOM extensions represent a large portion of where you'll spend
your time. Prototype adds many convenience methods to elements returned by
$ function. For instance, you can write
to get the element with the ID of
comments, add a class name to it, and
show it (if it was previously hidden).
In other words, Prototype adds "instance" methods to DOM nodes. This is made possible by direct extension of the backing DOM objects (in browsers that support it) and by manual extension of individual nodes (in browsers that do not).