你的浏览器完全支持classList (DOMTokenList)

classList (DOMTokenList ) :

The classList API provides methods and properties to manage class names of DOM elements. Using it, we can perform operations such as adding and removing classes, or checking if a given class is present on an element.

该API使用，见下面demo

该API被支持的情况下，可以正常调用方法，log输出有效结果，否则log不输出任何内容

classList API

Live sample element

Play area

Log