https://blog.csdn.net/qq_43537721/article/details/99713375?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-6.control&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-6.control
https://blog.csdn.net/moses_binson/article/details/83055961?utm_medium=distribute.pc_relevant.none-task-blog-baidujs_baidulandingword-3&spm=1001.2101.3001.4242
CSS3选择器再CSS2.1选择器的基础上增加了属性选择器、伪类选择器、过滤选择器，减少了对HTML类名或ID名的依赖，避免了对HTML结构的干扰，让编写代码更加轻松。
