html--结构伪类选择器

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
        child 孩子  向下寻找时，没有找到指定元素，则不会在寻找
        type  类型  向下寻找时，没有找到指定元素，继续往下寻找，直到找到
        从(1)开始搜索
        nth-child(值)   nth-of-type(值) 寻找指定值  n=所有  偶数2，4，6…… 基数：1，3，5……如下，可运行
        first-of-type  寻找第一个元素   last-of-type 寻找最后一个元素  only-of-type  寻找唯一元素
         
        <style>
/*          li:nth-child(2n+1){
                background-color: #FF0000;
            }
            li:nth-of-type(2n){
                background-color: blue;
            } */
/*          li:nth-of-type(2){
                background-color: aqua;
            }
            li:nth-child(5){
                background-color: chocolate;
            } */
            li:first-of-type{
                background-color: #FF0000;
            }
            li:last-child{
                background-color: #FF0000;
            }
            p:only-of-type{
                color: blue;
            }
/*          div:only-of-type{
                background-color: #FF0000;
            } */
        </style>
    </head>
    <body>
        <ul>
            <div>aaa</div>
            <li></li>
            <li></li>
            <div>aaa</div>
            <li></li>
            <li></li>
            <li></li>
            <p>111</p>
        </ul>
<!--         <ul>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
        </ul> -->
    </body>
</html>