CSS3选择器（全）_html/css_WEB-ITnose
CSS选择器复习
通用选择器：* 选择到所有的元素
选择子元素：> 选择到元素的直接后代(第一级子元素)
相邻兄弟选择器：+ 选择到紧随目标元素后的第一个元素
普通兄弟选择器：~ 选择到紧随其后的所有兄弟元素
伪元素选择器：
::first-line 匹配文本块的首行
::first-letter 选择文本块的首字母
伪类选择器：
:before, :after在元素内容前面、后面添加内容(相当于行内元素)
CSS3结构选择器
:nth-child 选择指定索引处的子元素
nth-child(n) 父元素下的第n个子元素
nth-child(odd) 奇数子元素(同nth-child(2n-1))
nth-child(even) 偶数子元素(同nth-child(2n))
nth-child(an+b) 公式
(nth-child从1开始)
:nth-last-child(n) 倒数第n个子元素
:nth-of-type(n) 父元素下的第n个指定类型的子元素
:nth-last-of-type 父元素下的倒数第n个指定类型的子元素
:first-child 选择父元素下的第一个子元素
:last-child 选择父元素下的最后一个子元素
:only-child 选择父元素下唯一的子元素
:only-of-type 选择父元素下指定类型的唯一子元素
:root 选择文档的根目录，返回html
div :only-child注意空格（选中div下唯一的子元素）
伪类选择器
:link指向未被访问页面的链接设置样式
:visited设置指向已访问页面的链接的样式
:hover鼠标悬停时触发
:active在点击时触发
:enabled 选择启用状态元素
:disabled 选择禁用状态元素
:checked 选择被选中的input元素（单选按钮或复选框）
:default 选择默认元素
:valid、invalid 根据输入验证选择有效或无效的input元素
:in-range、out-of-range 选择指定范围之内或者之外受限的元素
:repuired、optional 根据是否允许:required属性选择input元素
如果将link的颜色设置的与visited相同，则页面打开时，link的样式被visited样式覆盖，如上，a标签显示的字体颜色为绿色。
但是如果设置为不同的属性，可以呈现出叠加的效果。
点击a标签时，字体的颜色为黄色。
利用label修改radio的样式：如下：
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="Keywords" content="关键词一，关键词二"> <meta name="Description" content="网站描述内容"> <meta name="Author" content="刘艳"> <title></title> <style> input[type="radio"]{display: none;} label{display: inline-block;width: 24px;height: 24px; border-radius: 50%;border: 1px solid #ccc;margin: 5px;} :checked + label{background: #00b3ee;} </style></head><body> <input type="radio" name = "fruit" id = "check1"/> <label for="check1"></label> <input type="radio" name = "fruit" id = "check2"/> <label for="check2"></label> <input type="radio" name = "fruit" id = "check3"/> <label for="check3"></label> <input type="radio" name = "fruit" id = "check4"/> <label for="check4"></label></body></html>实现的效果：
:default
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="Keywords" content="关键词一，关键词二"> <meta name="Description" content="网站描述内容"> <meta name="Author" content="刘艳"> <title></title> <style> :default{background: #009FE6;} </style></head><body> <form> <input type="text"> <button>按钮</button> <input type="submit" value="提交"> </form></body></html>form表单中默认获取到焦点的是Button按钮
属性选择器
E[attr] 属性名，不确定具体属性值
E[attr=”value”] 指定属性名，并指定其对应属性值
E[attr ~=”value”] 指定属性名，找到的是具有此属性名，且与其它属性名之间用空格隔开，如下：
E[attr ^= “value”] 指定属性名，属性值以value开头
E[attr $=”value”] 指定属性名，属性值以value结束
E[attr *=”value”] 指定了属性名，属性值中包含了value
E[attr |= “value”] 指定属性名，属性值以value-开头或者值为value
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