This preprocessor constant yields true if the script is running in a genuine Microsoft JScript interpreter, and NaN if it is JavaScript but not JScript.

These directives may have been defined with a @ symbol rather than a # symbol for reasons of consistency across a variety of Microsoft platforms. Therefore, this directive may be useful to be able to conditionally include script source that depends on the kind of interpreter being used.

For now this directive will always return the true value when used in the MSIE browser.

If you intend to hide this directive inside some comments, it must be done like this:

/*@_jscript @*/