Macromedia Flash Professional 8 UNLEASHED [Electronic resources] نسخه متنی

Undefined Data Type

Much like null, undefined represents the absence of data. However, unlike null, undefined can be assigned in several ways:

• It can be manually assigned in the Actions panel.

• The interpreter will assign it if a variable does not exist.

• The interpreter will assign it if a variable has no value.

Let's take a look at the undefined data type in action.

var myTitle_str:String;
trace (typeof(myTitle_str));
// output: undefined

Like null, because undefined represents the absence of data, it is only equal to itself and null.