Learn how to add, remove and test for CSS classes using the classList API. It‘s more powerful than using className and doesn‘t require any dependencies.
https://gist.run/embed.html?id=9feda23aeb6ddd1b47e33f38e1518aaa
[Javascript] Manipulate the DOM with the classList API
原文：http://www.cnblogs.com/Answer1215/p/5880260.html