kristopolous/Porter-Stemmer — pull request #4 by albertsun (2012-09-06 22:43:51+00:00)
Title: Use hasOwnProperty to test if property exists

Trying things like:

stemmer("__proto__")

Or in Firefox

stemmer("watch")

Or other things that are properties of an object instance (https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object) and the stemmer will return the object function instead of a string.