Sorry Ashley for being unclear and jumping to solutions before making the requirements clear. What I want has nothing to do with extern.js but I saw it as a possible solution to my needs.
What I want is:
* Code completion in Webstorm when using external libraries in a plugin.
As code completion is built on "dot" syntax it doesn't work when using literals. Another thing is that JSLint/JSHint complains about this, minor issue but I couldn't get Bracket to work after their last update.
Any suggestions?