Whenever possible, put your ActionScript® in a single location. Organizing your code in one place helps you edit projects more efficiently, because you can avoid searching in different places when you debug or modify the ActionScript. If you put code in a FLA file, put ActionScript on Frame 1 or Frame 2 in a layer called actions on the topmost layer in the Timeline. Alternatively, you might put all of your code in ActionScript files. Some Flash Professional applications do not always put all code in a single place (in particular, ActionScript 2.0-based applications that use screens or behaviors).

You can usually put all your code in the same location (on a frame, or in ActionScript files), with the following advantages:

• Code is easy to find in a potentially complex source file.

• Code is easy to debug.

Avoid attaching ActionScript to objects in a FLA file, even in simple SWF files. (Only ActionScript 1.0 and 2.0. can be attached to objects; ActionScript 3.0 cannot.) Attaching code to an object means that you select a movie clip, component, or button instance; open the Actions panel; and add ActionScript using the on() or onClipEvent() handler functions.

Attaching ActionScript code to objects is strongly discouraged for the following reasons:

• It is difficult to locate, and the FLA files are difficult to edit.

• It is difficult to debug.

• ActionScript that is written on the timeline or in classes is more elegant and easier to build upon.

• It encourages poor coding style.

• The contrast between two styles of coding can be confusing to people learning ActionScript; it forces students and readers to learn different coding styles, additional syntax, and a poor and limited coding style.

  Avoid attaching ActionScript 2.0 to a button called myButton_btn, which looks like the following:

  on (release) { 
      //do something 
  }

  However, placing ActionScript 2.0 with the same purpose on the timeline (which is encouraged), looks like the following code:

  myButton_btn.onRelease = function() { 
      //do something 
  };

  Note: Different practices apply when using behaviors, which sometimes involves attaching code to objects.