Dynamic HTML: The Definitive Reference

About Static Objects

Unlike the heavily object-oriented Java language, there is little of the traditional object-oriented vernacular in the object-based JavaScript language. As a result, scripters tend not to think in terms of static objects and object instantiation. But some of that does take place behind the scenes.

Some core language objects act as if they were true static objects. The Math object is a good example; it contains a number of properties and methods that scripts use without ever having to “peel off” an instance of that object to do some math.

In contrast, the Date object is a static object that generates an instance of itself each time someone creates a new date:

var now = new Date()

In this example, the now variable is an instance of the Date object—a snapshot of the object frozen in time. That instance provides access to many methods that let scripts get pieces of date and time, as well as set new values to those pieces. The methods actually “live” in the static object, but you access them through the instance that holds a value that can be influenced by those methods (yes, these methods are inherited, but JavaScript doesn’t use this term much). Only on rare occasions do scripts ever need to look directly at the static Date object for other kinds of assistance (such as the getTimezoneOffset() method).

Most objects are either all static (Math) or completely suppress themselves from the scene once you create instances you work with (String, Array, Number). Only a few ...