MACROMEDIA FLASH MX 2004-ACTIONSCRIPT LANGUAGE Reference page 280

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
Usage 4: The following example shows the behavior of on object references:
delete
var ref1:Object = new Object();
ref1.name = "Jody";
// copy the reference variable into a new variable
// and delete ref1
ref2 = ref1;
delete ref1;
trace("ref1.name "+ref1.name); //output: undefined
trace("ref2.name "+ref2.name); //output: Jody
If had not been copied into , the object would have been deleted when was
ref1 ref2 ref1
deleted because there would be no references to it. If you delete , there are no references to
ref2
the object; it will be destroyed, and the memory it used becomes available.
See also
var
280 Chapter 2: ActionScript Language Reference