content
CSS
property replaces an element with a generated value. Objects inserted using the
content
property are
anonymous
replaced elements
.
/* Keywords that cannot be combined with other values */
content: normal;
content: none;
/* <image> values */
content: url("http://www.example.com/test.png");
content: linear-gradient(#e66465, #9198e5);
/* alt text for generated content, added in the Level 3 specification */
content: url("http://www.example.com/test.png") / "This is the alt text";
/* values below can only be applied to generated content using ::before and ::after */
/* <string> value */
content: "prefix";
/* <counter> values, optionally with <list-style-type> */
content: counter(chapter_counter);
content: counter(chapter_counter, upper-roman);
content: counters(section_counter, ".");
content: counters(section_counter, ".", decimal-leading-zero);
/* attr() value linked to the HTML attribute value */
content: attr(value string);
/* Language- and position-dependent keywords */
content: open-quote;
content: close-quote;
content: no-open-quote;
content: no-close-quote;
/* Except for normal and none, several values can be used simultaneously */
content: open-quote chapter_counter;
/* Global values */
content: inherit;
content: initial;
content: unset;
none
The pseudo-element is not generated.
normal
none
为
::before
and
::after
pseudo-elements.
<string>
\000A9
represents the copyright symbol.
<image>
<image>
, denoted by the
<url>
or
<gradient>
data type, or part of the webpage, defined by the
element()
function, denoting the content to display.
<counter>()
<counter-reset>
and
<counter-increment>
properies. It can be displayed using either the
counter()
or
counters()
函数。
counter()
function has two forms: 'counter(
name
)' or 'counter(
name
, style)'. The generated text is the value of the innermost counter of the given name in scope at the given pseudo-element. It is formatted in the specified
<list-style-type>
(
decimal
by default).
counters()
function also has two forms: 'counters(
name
,
string
)' or 'counters(
name
,
string
,
style
)'. The generated text is the value of all counters with the given name in scope at the given pseudo-element, from outermost to innermost, separated by the specified string. The counters are rendered in the indicated
<list-style-type>
(
decimal
by default).
attr(x)
x
as a string. If there is no attribute
x
, an empty string is returned. The case-sensitivity of attribute names depends on the document language.
open-quote
|
close-quote
quotes
特性。
no-open-quote
|
no-close-quote
Introduces no content, but increments (decrements) the level of nesting for quotes.
CSS-generated content is not included in the DOM . Because of this, it will not be represented in the accessibility tree and certain assistive technology/browser combinations will not announce it. If the content conveys information that is critical to understanding the page's purpose, it is better to include it in the main document.
| 初始值 |
normal
|
|---|---|
| 适用于 |
::before
and
::after
pseudo-elements
|
| 继承 | no |
| 计算值 |
On elements, always computes to
normal
. On
::before
and
::after
, if
normal
is specified, computes to
none
. Otherwise, for URI values, the absolute URI; for
attr()
values, the resulting string; for other keywords, as specified.
|
| 动画类型 | discrete |
normal | none | [ <content-replacement> | <content-list> ] [/ <string> ]?where
<content-replacement> = <image>
<content-list> = [ <string> | contents | <image> | <quote> | <target> | <leader()> ]+where
<image> = <url> | <image()> | <image-set()> | <element()> | <paint()> | <cross-fade()> | <gradient>
<quote> = open-quote | close-quote | no-open-quote | no-close-quote
<target> = <target-counter()> | <target-counters()> | <target-text()>
<leader()> = leader( <leader-type> )where
<image()> = image( <image-tags>? [ <image-src>? , <color>? ]! )
<image-set()> = image-set( <image-set-option># )
<element()> = element( <id-selector> )
<paint()> = paint( <ident>, <declaration-value>? )
<cross-fade()> = cross-fade( <cf-mixing-image> , <cf-final-image>? )
<gradient> = <linear-gradient()> | <repeating-linear-gradient()> | <radial-gradient()> | <repeating-radial-gradient()> | <conic-gradient()>
<target-counter()> = target-counter( [ <string> | <url> ] , <custom-ident> , <counter-style>? )
<target-counters()> = target-counters( [ <string> | <url> ] , <custom-ident> , <string> , <counter-style>? )
<target-text()> = target-text( [ <string> | <url> ] , [ content | before | after | first-letter ]? )
<leader-type> = dotted | solid | space | <string>where
= ltr | rtl
<image-src> = <url> | <string>
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
<image-set-option> = [ <image> | <string> ] <resolution>
<id-selector> = <hash-token>
<cf-mixing-image> = <percentage>? && <image>
<cf-final-image> = <image> | <color>
<linear-gradient()> = linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<repeating-linear-gradient()> = repeating-linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<radial-gradient()> = radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )
<repeating-radial-gradient()> = repeating-radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )
<conic-gradient()> = conic-gradient( [ from <angle> ]? [ at <position> ]?, <angular-color-stop-list> )
<counter-style> = <counter-style-name> | symbols()where
<rgb()> = rgb( <percentage>{3} [ / <alpha-value> ]? ) | rgb( <number>{3} [ / <alpha-value> ]? ) | rgb( <percentage>#{3} , <alpha-value>? ) | rgb( <number>#{3} , <alpha-value>? )
<rgba()> = rgba( <percentage>{3} [ / <alpha-value> ]? ) | rgba( <number>{3} [ / <alpha-value> ]? ) | rgba( <percentage>#{3} , <alpha-value>? ) | rgba( <number>#{3} , <alpha-value>? )
<hsl()> = hsl( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsl( <hue>, <percentage>, <percentage>, <alpha-value>? )
<hsla()> = hsla( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsla( <hue>, <percentage>, <percentage>, <alpha-value>? )
<side-or-corner> = [ left | right ] || [ top | bottom ]
<color-stop-list> = [ <linear-color-stop> [, <linear-color-hint>]? ]# , <linear-color-stop>
<ending-shape> = circle | ellipse
<size> = closest-side | farthest-side | closest-corner | farthest-corner | <length> | <length-percentage>{2}
<position> = [ [ left | center | right ] || [ top | center | bottom ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]? | [ [ left | right ] <length-percentage> ] && [ [ top | bottom ] <length-percentage> ] ]
<angular-color-stop-list> = [ <angular-color-stop> [, <angular-color-hint>]? ]# , <angular-color-stop>
<counter-style-name> = <custom-ident>where
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>
<linear-color-stop> = <color> <color-stop-length>?
<linear-color-hint> = <length-percentage>
<length-percentage> = <length> | <percentage>
<angular-color-stop> = <color> && <color-stop-angle>?
<angular-color-hint> = <angle-percentage>where
<color-stop-length> = <length-percentage>{1,2}
<color-stop-angle> = <angle-percentage>{1,2}
<angle-percentage> = <angle> | <percentage>
This example inserts quotation marks around quotes, and adds the word "Chapter" before headings.
<h1>5</h1>
<p>According to Sir Tim Berners-Lee,
<q cite="http://www.w3.org/People/Berners-Lee/FAQ.html#Internet">I was
lucky enough to invent the Web at the time when the Internet
already existed - and had for a decade and a half.</q>
We must understand that there is nothing fundamentally wrong
with building on the contributions of others.
</p>
<h1>6</h1>
<p>According to the Mozilla Manifesto,
<q cite="http://www.mozilla.org/en-US/about/manifesto/">Individuals
must have the ability to shape the Internet and
their own experiences on the Internet.</q>
Therefore, we can infer that contributing to the open web
can protect our own individual experiences on it.
</p>
q {
color: blue;
}
q::before {
content: open-quote;
}
q::after {
content: close-quote;
}
h1::before {
content: "Chapter "; /* The trailing space creates separation
between the added content and the
rest of the content */
}
This example inserts an image before the link. If the image is not found, it inserts text instead.
<a href="http://www.mozilla.org/en-US/">Mozilla Home Page</a>
a::before {
content: url("https://mozorg.cdn.mozilla.net/media/img/favicon.ico") / " MOZILLA: ";
font: x-small Arial, sans-serif;
color: gray;
}
This example inserts additional text after special items in a list.
<h2>Paperback Best Sellers</h2> <ol> <li>Political Thriller</li> <li class="new-entry">Halloween Stories</li> <li>My Biography</li> <li class="new-entry">Vampire Romance</li> </ol>
.new-entry::after {
content: " New!"; /* The leading space creates separation
between the added content and the
rest of the content */
color: red;
}
This example inserts an image before each link, and adds its
id
attribute after.
<ul>
<li><a id="moz" href="http://www.mozilla.org/">
Mozilla Home Page</a></li>
<li><a id="mdn" href="https://developer.mozilla.org/">
Mozilla Developer Network</a></li>
</ul>
a {
text-decoration: none;
border-bottom: 3px dotted navy;
}
a::after {
content: " (" attr(id) ")";
}
#moz::before {
content: url("https://mozorg.cdn.mozilla.net/media/img/favicon.ico");
}
#mdn::before {
content: url("https://mdn.mozillademos.org/files/7691/mdn-favicon16.png");
}
li {
margin: 1em;
}
This example replaces an element's content with an image. You can replace the contents of an element with either a
<url>
or an
<image>
value. Content added with
::before
or
::after
will not be generated as the contents of the element have been replaced.
<div id="replaced">Mozilla</div>
#replaced {
content: url("https://mdn.mozillademos.org/files/12668/MDN.svg");
}
#replaced::after { /* will not show if element replacement is supported */
content: " (" attr(id) ")";
}
| 规范 | 状态 | 注释 |
|---|---|---|
|
CSS Generated Content Module Level 3
The definition of 'content' in that specification. |
工作草案 | Adds support for alt-text |
|
CSS Level 2 (Revision 1)
The definition of 'content' in that specification. |
推荐 | 初始定义 |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
content
|
Chrome 完整支持 1 | Edge 完整支持 12 | Firefox 完整支持 1 | IE 完整支持 8 | Opera 完整支持 4 | Safari 完整支持 1 | WebView Android 完整支持 1 | Chrome Android 完整支持 18 | Firefox Android 完整支持 4 | Opera Android 完整支持 10.1 | Safari iOS 完整支持 1 | Samsung Internet Android 完整支持 1.0 |
Alternative text after
/
|
Chrome 完整支持 77 | Edge 完整支持 79 | Firefox 不支持 No | IE 不支持 No | Opera 完整支持 64 | Safari 不支持 No | WebView Android 完整支持 77 | Chrome Android 完整支持 77 | Firefox Android 不支持 No | Opera Android 完整支持 55 | Safari iOS 不支持 No | Samsung Internet Android 完整支持 12.0 |
| Element replacement | Chrome 完整支持 28 | Edge 完整支持 79 | Firefox 完整支持 63 | IE 不支持 No | Opera 完整支持 7 | Safari 完整支持 9 | WebView Android 完整支持 ≤37 | Chrome Android 完整支持 28 | Firefox Android 完整支持 63 | Opera Android 完整支持 10.1 | Safari iOS 完整支持 9 | Samsung Internet Android 完整支持 1.5 |
url()
|
Chrome 完整支持 1 | Edge 完整支持 12 | Firefox 完整支持 1 | IE 完整支持 8 | Opera 完整支持 7 | Safari 完整支持 1 | WebView Android 完整支持 37 | Chrome Android 完整支持 18 | Firefox Android 完整支持 4 | Opera Android 完整支持 14 | Safari iOS 完整支持 1 | Samsung Internet Android 完整支持 1.0 |
完整支持
不支持
content
quotes