Flash CS3 Documentation

Learning ActionScript 2.0 in Adobe Flash > Data and Data Types > About variables > About naming variables

About naming variables

Be careful when you start naming variables, because although they can have nearly any name, there are some rules. A variable's name must follow these rules:

• A variable must be an identifier.

  NOTE

  An identifier is the name of a variable, property, object, function, or method. The first character of an indentifier must be a letter, underscore (_), or dollar sign ($). Each subsequent character can be a number, letter, underscore, or dollar sign.

• A variable cannot be a keyword or an ActionScript literal such as true, false, null, or undefined. For more information on literals, see About literals.
• A variable must be unique within its scope (see About variables and scope).
• A variable should not be any element in the ActionScript language, such as a class name.

If you don't follow the rules when you name a variable, you might experience syntax errors or unexpected results. In the following example, if you name a variable new and then test your document, Flash will generate a compiler error:

// This code works as expected.
var helloStr:String = new String();
trace(helloStr.length); // 0
// But if you give a variable the same name as a built-in class...
var new:String = "hello"; //error: Identifier expected
var helloStr:String = new String();
trace(helloStr.length); // undefined

The ActionScript editor supports code hints for built-in classes and for variables that are based on these classes. If you want Flash to provide code hints for a particular object type that you assign to a variable, you can strictly type the variable. Code hints provide tooltip-style syntax hints and a pop-up menu that helps you write your code quickly.

For example, type the following code:

var members:Array = new Array();
members.

As soon as you type the period (.) in the Actions panel, Flash displays a list of methods and properties available for Array objects.

For recommended coding conventions for naming variables, see Naming variables.

Flash CS3