WebStorm 7.0.0 Web Help  Among the rather simple use-cases, like
having detailed syntax checks for all kinds of "micro-languages"
that are used e.g. in Pattern.compile(), XPath.compile() and so
on, here are some less obvious, yet very useful examples how
IntelliLang can leverage WebStorm's support for a much better
coding assistance.  The new scripting support in the upcoming
Java 1.6 is another case where it will be important to get as
much as possible edit-time assistance when script-code is
constructed from Java code.  Extended JavaScript support  When
dealing with JavaScript that's not directly embedded inside an
HTML page, WebStorm usually just treats it as plain text.
Consider the following example that creates an HTML page from an
XSLT script. Without the JavaScript language being injected into
the script tag with the XHTML namespace as shown in the
screenshot below, this would be treated as plain text, with no
further code assistance.   Support for JSP custom cags  With
IntelliLang it's also possible