Constants
31
In files published for Flash Player 6 or earlier, the value of
Number(undefined)
is
0
. In files
published for Flash Player 7 or later, the value of
Number(undefined)
is
NaN
.
The value
undefined
is similar to the special value
null
. When
null
and
undefined
are
compared with the equality (
==
) operator, they compare as equal. However, when
null
and
undefined
are compared with the strict equality (
===
) operator, they compare as not equal.
Availability:
ActionScript 1.0; Flash Lite 1.1
Example
In the following example, the variable
x
has not been declared and therefore has the value
undefined
.
In the first section of code, the equality operator (
==
) compares the value of
x
to the value
undefined
, and the appropriate result is sent to the Output panel. In the first section of code,
the equality operator (
==
) compares the value of
x
to the value
undefined
, and the
appropriate result is sent to the log file.
In the second section of code, the equality (
==
) operator compares the values
null
and
undefined
.
// x has not been declared
trace("The value of x is "+x);
if (x == undefined) {
trace("x is undefined");
} else {
trace("x is not undefined");
}
trace("typeof (x) is "+typeof (x));
if (null == undefined) {
trace("null and undefined are equal");
} else {
trace("null and undefined are not equal");
}
The following result is displayed in the Output panel.
The value of x is undefined
x is undefined
typeof (x) is undefined
null and undefined are equal
Summary of Contents for FLASHLITE2 ACTIONSCRIPT-LANGUAGE
Page 1: ...Flash Lite 2 x ActionScript Language Reference...
Page 22: ...22 Contents...
Page 244: ...244 ActionScript language elements...
Page 760: ...760 ActionScript classes...
