20.3. Built-in Classes and Objects
This Language Reference assumes that you understand the terms class, object, and instance as discussed exhaustively in Chapter 12, "Objects and Classes". The built-in classes of ActionScript are used to create objects that can control a movie and manipulate data. The built-in ActionScript classes are Array, Boolean, Color, Date, MovieClip, Number, Object, Sound, String, XML, XMLNode, and XMLSocket. To create an instance of a particular class, we use the class's constructor function with the new operator. For example, to make a new object of the Color class, we use the Color constructor as follows:
myColor = new Color(_root);
For each class in the Language Reference, the Constructor entry shows how to create new objects of that particular class (i.e., it demonstrates each class's constructor function syntax). The properties, methods, and event handlers available for objects in the class are also summarized along with a description of the class's purpose and typical use. Some classes also define methods or properties that are accessed through the class constructor itself, not individual instances. These methods and properties are listed as Class Methods and Class Properties. Full details for each class's properties, methods, and event handlers are given in an alphabetical list after each class's general introduction.
ActionScript's special built-in objects -- Arguments, Key, Math, Mouse and Selection -- are interspersed alphabetically with the class descriptions in this book but are distinguished by the word Object (e.g., Math Object). Unlike true classes, which use a constructor function to instantiate multiple objects, these standalone objects are never instantiated (i.e., they are not constructed with the new operator). Rather, they are predefined objects that exist solely to collect related functionality into a single package. The Math object, for example, provides convenient access to common mathematical functions and constants.
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