CSS3的content属性详解

电玩女神 2022-08-05 00:42 233阅读 0赞

CSS中主要的伪元素有四个：before/after/first-letter/first-line，在before/after伪元素选择器中，有一个content属性，能够实现页面中的内容插入。

### 插入纯文字 ###

content:”插入的文章”，或者content:none不插入内容  
html:

css

h1::after{ content:"h1后插入内容" }
    h2::after{ content:none }

运行结果：[https://jsfiddle.net/dwqs/Lmm1r08x/][https_jsfiddle.net_dwqs_Lmm1r08x]

### 嵌入文字符号 ###

可以使用content属性的open-quote属性值和close-quote属性值在字符串两边添加诸如括号、单引号、双引号之类的嵌套文字符号。open-quote用于添加开始的文字符号，close-quote用于添加结束的文字符号。修改上述的css:

h1{ quotes:"(" ")"; /*利用元素的quotes属性指定文字符号*/ }
    h1::before{ content:open-quote; }
    h1::after{ content:close-quote; }
    h2{ quotes:"\"" "\""; /*添加双引号要转义*/ }
    h2::before{ content:open-quote; }
    h2::after{ content:close-quote; }

运行结果：[https://jsfiddle.net/dwqs/p8e3qvv4/][https_jsfiddle.net_dwqs_p8e3qvv4]

### 插入图片 ###

content属性也可以直接在元素前/后插入图片  
html:

css:

h3::after{ content:url(http://ido321.qiniudn.com/wp-content/themes/yusi1.0/img/new.gif) }

运行结果：[https://jsfiddle.net/dwqs/c6qk6pkv/][https_jsfiddle.net_dwqs_c6qk6pkv]

### 插入元素的属性值 ###

content属性可以直接利用attr获取元素的属性，将其插入到对应位置。  
html:

css:

a:after{ content:attr(href); }

运行结果：[https://jsfiddle.net/dwqs/m220nzan/][https_jsfiddle.net_dwqs_m220nzan]

### 插入项目编号 ###

利用content的counter属性针对多个项目追加连续编号.  
html:

css:

h1:before{ content:counter(my)'.'; }
    h1{ counter-increment:my; }

运行结果：[https://jsfiddle.net/dwqs/2ueLg3uj/][https_jsfiddle.net_dwqs_2ueLg3uj]

### 项目编号修饰 ###

默认插入的项目编号是数字型的，1,2,3.。。。自动递增，也能给项目编号追加文字和样式,依旧利用上面的html，css修改如下：

h1:before{ content:'第'counter(my)'章'; color:red; font-size:42px; }
    h1{ counter-increment:my; }

运行结果：[https://jsfiddle.net/dwqs/17hqznca/][https_jsfiddle.net_dwqs_17hqznca]

### 指定编号种类 ###

利用content(计数器名，编号种类)格式的语法指定编号种类，编号种类的参考可以依据ul的list-style-type属性值。利用上述的html，css修改如下：

h1:before{ content:counter(my,upper-alpha); color:red; font-size:42px; }
    h1{ counter-increment:my; }

运行结果：[https://jsfiddle.net/dwqs/4nsrtxup/][https_jsfiddle.net_dwqs_4nsrtxup]

### 编号嵌套 ###

大编号中嵌套中编号，中编号中嵌套小编号。  
html:

css:

h1::before{ content:counter(h)'.'; }
    h1{ counter-increment:h; }
    p::before{ content:counter(p)'.'; margin-left:40px; }
    p{ counter-increment:p; }

运行结果：[https://jsfiddle.net/dwqs/2k5qbz51/][https_jsfiddle.net_dwqs_2k5qbz51]  
在示例的输出中可以发现，p的编号是连续的。如果对于每一个h1后的三个p重新编号的话，可以使用counter-reset属性重置，修改上述h1的css:

h1{ counter-increment:h; counter-reset:p; }

这样，编号就重置了，看看结果：[https://jsfiddle.net/dwqs/hfutu4Lq/][https_jsfiddle.net_dwqs_hfutu4Lq]  
还可以实现更复杂的嵌套，例如三层嵌套。  
html:

css:

h1::before{ content:counter(h1)'.'; }
    h1{ counter-increment:h1; counter-reset:h2; }
    h2::before{ content:counter(h1) '-' counter(h2); }
    h2{ counter-increment:h2; counter-reset:h3; margin-left:40px; }
    h3::before{ content:counter(h1) '-' counter(h2) '-' counter(h3); }
    h3{ counter-increment:h3; margin-left:80px; }

运行结果：[https://jsfiddle.net/dwqs/wuuckquy/][https_jsfiddle.net_dwqs_wuuckquy]

张大大有一篇利用counter实现计数的文章：[小tip:CSS计数器+伪类实现数值动态计算与呈现][tip_CSS]

原文：[http://www.ido321.com/1555.html][http_www.ido321.com_1555.html]

[https_jsfiddle.net_dwqs_Lmm1r08x]: https://jsfiddle.net/dwqs/Lmm1r08x/
[https_jsfiddle.net_dwqs_p8e3qvv4]: https://jsfiddle.net/dwqs/p8e3qvv4/
[https_jsfiddle.net_dwqs_c6qk6pkv]: https://jsfiddle.net/dwqs/c6qk6pkv/
[https_jsfiddle.net_dwqs_m220nzan]: https://jsfiddle.net/dwqs/m220nzan/
[https_jsfiddle.net_dwqs_2ueLg3uj]: https://jsfiddle.net/dwqs/2ueLg3uj/
[https_jsfiddle.net_dwqs_17hqznca]: https://jsfiddle.net/dwqs/17hqznca/
[https_jsfiddle.net_dwqs_4nsrtxup]: https://jsfiddle.net/dwqs/4nsrtxup/
[https_jsfiddle.net_dwqs_2k5qbz51]: https://jsfiddle.net/dwqs/2k5qbz51/
[https_jsfiddle.net_dwqs_hfutu4Lq]: https://jsfiddle.net/dwqs/hfutu4Lq/
[https_jsfiddle.net_dwqs_wuuckquy]: https://jsfiddle.net/dwqs/wuuckquy/
[tip_CSS]: http://www.zhangxinxu.com/wordpress/2014/12/css-counters-pseudo-class-checked-numbers/
[http_www.ido321.com_1555.html]: http://www.ido321.com/1555.html