ActionScript 2.0 Language Reference - Adobe Help and Support

null constant
A special value that can be assigned to variables or returned by a function if no data was
provided. You can use null to represent values that are missing or that do not have a defined
data type.
Availability: ActionScript 1.0; Flash Player 5
Example
The following example checks the first six values of an indexed array and outputs a message if
no value is set (if the value == null):
var testArray:Array = new Array();
testArray[0] = "fee";
testArray[1] = "fi";
testArray[4] = "foo";
for (i = 0; i < 6; i++) {
if (testArray[i] == null) {
trace("testArray[" + i + "] == null");
}
}
The output is the following:
testArray[2] == null
testArray[3] == null
testArray[5] == null
true constant
A unique Boolean value that represents the opposite of false. When automatic data typing
converts true to a number, it becomes 1; when it converts true to a string, it becomes
"true".
Availability: ActionScript 1.0; Flash Player 5
Example
The following example shows the use of true in an if statement:
var shouldExecute:Boolean;
// ...
// code that sets shouldExecute to either true or false goes here
// shouldExecute is set to true for this example:
shouldExecute = true;
40 ActionScript language elements