MACROMEDIA FLASH 8-FLASH LITE 2.X ACTIONSCRIPT LANGUAGE Reference page 188

The operator can fail and return if the parameter does not exist or
delete false reference
cannot be deleted. You cannot delete predefined objects and properties, nor can you delete
variables that are declared within a function with the statement. You cannot use the
var
operator to remove movie clips.
delete
Availability: ActionScript 1.0; Flash Lite 2.0
Returns
- A Boolean value.
Boolean
Parameters
- The name of the variable or object to eliminate.
reference:Object
Example
Usage 1: The following example creates an object, uses it, and deletes it after it is no longer
needed:
var account:Object = new Object();
account.name = "Jon";
account.balance = 10000;
trace(account.name); //output: Jon
delete account;
trace(account.name); //output: undefined
Usage 2: The following example deletes a property of an object:
// create the new object "account"
var account:Object = new Object();
// assign property name to the account
account.name = "Jon";
// delete the property
delete account.name;
Usage 3: The following example deletes an object property:
var my_array:Array = new Array();
my_array[0] = "abc"; // my_array.length == 1
my_array[1] = "def"; // my_array.length == 2
my_array[2] = "ghi"; // my_array.length == 3
// my_array[2] is deleted, but Array.length is not changed
delete my_array[2];
trace(my_array.length); // output: 3
trace(my_array); // output: abc,def,undefined
188 ActionScript language elements