eligrey/classList.js — pull request #25 by acbabis (2014-07-02 21:11:03+00:00)
Title: Duplicate Class Support

When adding a class to an element in vanilla JS, some programmers will append the class to the className without checking if it already exists. While this may be bad practice, it is supported. I recommend checking for duplicates in case the polyfill is used with code that already has redundant classes.