Creates variables used with conditional compilation statements.
Conditional compilation is supported in Internet Explorer only, not in Windows Store apps.
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.