CSS之旅（3）：强大的伪选择器_html/css

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CSS之旅（3）：强大的伪选择器_html/css_WEB-ITnose

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Jun 21, 2016 am 09:11 AM

原文出处：一线码农

说到伪选择器，真的让我体会到了CSS的无比强大，强大到自己貌似都不认识CSS了，有点C# 6.0中一些语法糖带给我们的震撼。。。首先我们可以在VS里面提前预览一下。

可以看到，上面的伪类有很多很多，多的让我眼都快瞎了。。。下面就挑一些实用性比较强的说一说。

一 :nth-child 伪选择器

我们知道在jquery中有一种选择器叫做“子类选择器”，对应的有:nth-child，:first-child，:last-child，:only-child，这回在CSS中同样

可以办到，可以说一定程度上缓解了jquery的压力，下面简单举个例子。

<html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        ul li:nth-child(1) {            color: red;        }    </style></head><body>    <ul>        <li>1</li>        <li>2</li>        <li>3</li>        <li>4</li>        <li>5</li>        <li>6</li>    </ul></body>

可以看到，当我灌的是:nth-child(1)的时候，ul的第一个li的color已经变成red了，如果复杂一点的话，可以将1改成n，浏览器在解析css的伪类

选择器的时候，内部应该会调用相应的方法来解析到对应dom的节点，首先要明白n是从0，步长为1的递增，这个和jquery的nth-child类似，没

什么好说的，然后我们尝试下：first-child 和 last-child。

<html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        ul li:first-child {            color: red;            font-weight:800;        }        ul li:last-child {            color: blue;            font-weight: 800;        }    </style></head><body>    <ul>        <li>1</li>        <li>2</li>        <li>3</li>        <li>4</li>        <li>5</li>        <li>6</li>    </ul></body></html>

二 :checked，:unchecked,:disabled,:enabled

同样在jquery中，有一组选择器叫做“表单对象属性“，我们可以看看jquery的在线文档。

同样我们很开心的发现，在css中也存在这些属性。。。是不是开始有点醉了。。。还是先睹为快。

1. disabled,enabled

<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        input[type='text']:enabled {            border: 1px solid red;        }            input[type='text']:disabled {                border: 1px solid blue;            }    </style></head><body>    <form>        <input type="text" disabled="disabled" />        <input type="text"/>    </form></body></html>

2. checked,unchecked

<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        form input[type="radio"]:first-child:checked {            margin-left: 205px;        }    </style></head><body>    <form>        <input class="test" type="radio" value="女" /><span>女</span><br/>        <input class="test" type="radio" value="男" /><span>男</span>    </form></body></html>

3. selected

这个在css中虽然没有原装的，但是可以用option:checked来替代，比如下面这样。

<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        option:checked {            color: red;        }    </style></head><body>    <form>        <select>            <option>1</option>            <option>2</option>            <option>3</option>        </select>    </form></body></html>

三 empty伪选择器

这个选择器有点意思，在jquery中叫做”内容选择器“，就是用来寻找空元素的，如果玩转jquery的empty，这个也没有什么问题，

下面举个例子，让第一个空p的背景变色。

<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title></title>    <style type="text/css">        p:first-child{            width:500px;            height:20px;        }        p:empty {            background:red;        }    </style></head><body>    <p></p>    <p>他好</p></body></html>

四：not(xxx) 伪选择器

同样这个也是非常经典的not选择器，在jquery中叫做”基本选择器“，想起来了没有？？？

总的来说，当你看完上面这些，是不是觉得css3中已经融入了一些”脚本处理行为”，这种感觉就是那个css再也不是你曾今认识的那个css了。

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