Creates variables used with conditional compilation statements.
Conditional compilation is not supported in Internet Explorer 11 Standards mode and Windows 8.x Store apps. Conditional compilation is supported in Internet Explorer 10 Standards mode and in all earlier versions.
Examples of variable declarations look like this:
The following operators are supported in parenthesized expressions:
* / %
<< >> >>>
< <= > >=
== != === !==
& ^ |
&& | |
If a variable is used before it has been defined, its value is NaN. NaN can be checked for using the @if statement:
This works because NaN is the only value not equal to itself.