Function Literal

The second way to declare a function is to use an assignment statement with a function literal, which is also sometimes called an anonymous function. This is a more verbose method that is widely used in earlier versions of ActionScript.
An assignment statement with a function literal begins with the var keyword, followed by:

• the function name;
• the colon operator (:);
• the Function keyword used to indicate the data type;
• the assignment operator (=);
• the function keyword
• the parameters, in a comma-delimited list enclosed in parentheses;
• the function body, that is, the ActionScript code to be executed when the function is invoked, enclosed in curly braces.

For example, the following code declares the traceParameter function using a function literal:

var traceParameter:Function = function (aParam:String) {
     trace(aParam);
};
traceParameter("hello"); // Output: hello

Note that you do not specify a function name, as you do in a function statement. Another important difference between function literals and function statements is that a function literal is an expression rather than a statement. This means that a function literal cannot stand on its own, as a function statement can. A function literal can only be used as a part of a statement, usually an assignment statement. The following example shows a function literal assigned to an array element:

var traceArray:Array = new Array();
     traceArray[0] = function (aParam:String) {
     trace(aParam);
};
traceArray[0]("hello");