Module don't work along with webpack

[xiaoyuze88]

Because after processed by webpack, 'this' that passed to the factory function won't point to the global window, but an empty object {}, which makes window.document is undefined.

So when executing this line:
'onfocusin' in document, this error throws: Uncaught TypeError: Cannot use 'in' operator to search for 'onfocusin' in undefined.

Just change this to window can fix this (In NodeJS, this module won't work anyway, so it doesn't matter to pass window directly)

[xiaoyuze88]

This issue seems have already been fixed at v1.0.12, but v1.0.12 is not published to the npm, maybe this should be updated on npm, thanks a lot!