Introducing ActionScript

For this tutorial, we are going to begin to dig deeper into the Flash application. This will involve the introduction of ActionScript, offering some ideas on what it can be used for, the fun things that can be created, and an idea of what the future is going to be like with the scripting language. Flash can create very visually appealing sites or presentations, but with the introduction of ActionScript in version 4, the future suddenly seemed much brighter.

ActionScript is an object-oriented scripting language that helps to manipulate a Flash movie. While you will want to know some of the basics of ActionScript you don't need to understand every possible tool in order to start developing some scripts. You will quickly become more familiar with the language and thereby you can learn to create more complicated scripts and in turn more interactive Flash movies will result.

Just for a quick overview of what an object-oriented scripting language is, it means the ability to organize information by arranging it into groups that are called 'classes'. Multiple instances of a class are called objects, of which you can create your own or use the ones that are already defined inside of the ActionScript. When you create a class, you define all of the properties and the methods of each object that it in turn creates. The ActionScript language flows logically by executing the first statement and continuing in order until it reaches the final statement or a statement that tells ActionScript to go somewhere else.

With the introduction of Flash 5 came many new features and syntax that make it very similar to the JavaScript language. For the technical individuals that are reading this, ActionScript is based on the ECMA-262 (The European Computers Manufacturers Association) specification, which is an international standard for JavaScript. The Flash5ActionScript Web site has documentation and articles to help you understand the basics of ActionScript.

However, there are some major differences between the two languages. ActionScript doesn't support browser specific objects like document, anchor or window. It also doesn't completely support all of the JavaScript predefined objects. Of course the same is true in reverse. JavaScript doesn't support syntax from ActionScript such as tellTarget, ifFrameLoaded and others. ActionScript also doesn't support the Function constructor, or switch, continue, try, catch, throw, and statement labels. The eval action can only perform variable references. In JavaScript 'undefined' in a numeric context results in NaN, while in Flash 5 the result is '0'.

The ActionScript can be entered directly into the panel in the Expert Mode or, using Standard Mode, the user can choose elements from a pop-up menu or toolbox, similar to as it was done in version 4. The language supports five different data types, which are 'number', 'string', 'Boolean', 'Movie Clip' and 'object'. In version 4 there was the ability to use 'slash' syntax to set properties and methods of an object, but these are no longer preferred. There is now the 'dot' syntax to get and set the properties including movie clip instances and variables. You can also declare local variables that will expire at the end of an action list or a function call. This obviously allows you to manage memory better and also reuse variable names. In version 4 all variables were permanent — meaning even temporary variables like loop counters remained in the movie until it actually ended.

You can easily reuse blocks of code in your scripts, as you can define functions with parameters that will return variables. There are also predefined objects that allow you to access and manipulate certain types of information. A few examples include:

• The Date Object allows Flash to pick up the date and time information from whatever local computer is running the Flash file.
• The Mouse Object can hide the cursor so that you can actually create a custom cursor inside of the movie itself. Which could certainly confuse and perhaps frustrate people on a Web site if the arrow were to disappear.
• The Math Object contains a full range of built-in mathematical constants and functions. Such as cos (Cosine) and atan (Arctangent).
• The MovieClip Object allows you to control movie clips using various actions such as tellTarget, play, loadMovie or others. You can do this from an instance name by using the dot syntax (example – someMovieClip.play()).
• Finally the Sound Object is something that you can have fun with and allows you to add sounds to a movie, even adjust the sounds as it plays. There are ways to adjust the balance (setPan) and even the volume (setVolume)!
  Conclusion - Page 4
  Flash 5 Tutorial: Part 1
  Additional Features - Page 2