属性书写顺序
属性间顺序
常规情况下,属性的排序方式有这么几种方式:
- 随机
- 按字母序
- 按属性类型
- 按属性长度
国外著名的 Web 前端专家 Andy Ford 推荐过一种按照属性类型分组排序的方式,他把 CSS 属性分为 7 大类:
- 显示与浮动(
Diplay
&Flow
) - 定位(
Positioning
) - 尺寸(
Dimensions
) - 边框相关属性(
Margins
、Padding
、Borders
、Outline
) - 字体样式(
Typographic Styles
) - 背景(
Backgrounds
) - 其他样式(
Opacity、Cursors、Generated Content
)
这种按照样式类型分组排列的方式不仅把功能相似的属性归类到一起,并且按照样式功能的重要性从上到下进行了排序。可以把影响元素页面布局的样式(如 float
、margin
、padding
、height
、width
等)排到前面,而把不影响布局的样式(如background
、color
、font
等)放到后面。这种主次分明的排列方式,极大地提高了代码的可维护性。可参考文档Order of the Day: CSS Propertiesopen in new window,BTW,原文链接已经失效了,这一篇应该是有人之前复制过来的。
PS:个人认为,应该将 定位 放置在 显示与浮动 之前。
.example {
/* 显示与浮动 */
display: ;
visibility: ;
float: ;
clear: ;
/* 定位 */
position: ;
top: ;
right: ;
bottom: ;
left: ;
z-index: ;
/* 尺寸 */
box-sizing: ;
width: ;
min-width: ;
max-width: ;
height: ;
min-height: ;
max-height: ;
overflow: ;
/* 边框相关属性 */
margin: ;
margin-top: ;
margin-right: ;
margin-bottom: ;
margin-left: ;
padding: ;
padding-top: ;
padding-right: ;
padding-bottom: ;
padding-left: ;
border-width: ;
border-top-width: ;
border-right-width: ;
border-bottom-width: ;
border-left-width: ;
border-style: ;
border-top-style: ;
border-right-style: ;
border-bottom-style: ;
border-left-style: ;
border-color: ;
border-top-color: ;
border-right-color: ;
border-bottom-color: ;
border-left-color: ;
outline: ;
list-style: ;
table-layout: ;
caption-side: ;
border-collapse: ;
border-spacing: ;
empty-cells: ;
/* 字体样式 */
font: ;
font-family: ;
font-size: ;
line-height: ;
font-weight: ;
text-align: ;
text-indent: ;
text-transform: ;
text-decoration: ;
letter-spacing: ;
word-spacing: ;
white-space: ;
vertical-align: ;
color: ;
/* 背景 */
background: ;
background-color: ;
background-image: ;
background-repeat: ;
background-position: ;
/* 其他样式 */
opacity: ;
cursor: ;
content: ;
quotes: ;
}
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浏览器厂商前缀
.not-a-square {
-webkit-border-radius: 10px;
-moz-border-radius: 10px;
border-radius: 10px;
}
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始终将无前缀的标注属性放置在最后,因为浏览器厂商一开始在实现带前缀的属性时可能跟标准不一致,详见Ordering CSS3 Propertiesopen in new window
属性内顺序
background 属性简写
background
简写属性在一个声明中可设置所有的背景属性。
可设置属性如下:
background-image
: 设置背景图像, 可以是真实的图片路径, 也可以是创建的渐变背景;background-position
: 设置背景图像的位置;background-size
: 设置背景图像的大小;background-repeat
: 指定背景图像的铺排方式;background-attachment
: 指定背景图像是滚动还是固定;background-origin
: 设置背景图像显示的原点[background-position
相对定位的原点];background-clip
: 设置背景图像向外剪裁的区域;background-color
: 指定背景颜色。
简写的顺序如下: bg-color || bg-image || bg-position [ / bg-size]? || bg-repeat || bg-attachment || bg-origin || bg-clip
<bg-layer> =
<bg-image> ||
<bg-position> [ / <bg-size> ]? ||
<repeat-style> ||
<attachment> ||
<box> ||
<box>
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<final-bg-layer> =
<\'background-color'> ||
<bg-image> ||
<bg-position> [ / <bg-size> ]? ||
<repeat-style> ||
<attachment> ||
<box> ||
<box>
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The background property is a shorthand property for setting most background properties at the same place in the style sheet. The number of comma-separated items defines the number of background layers. Given a valid declaration, for each layer the shorthand first sets the corresponding layer of each of background-image, background-position, background-size, background-repeat, background-origin, background-clip and background-attachment to that property’s initial value, then assigns any explicit values specified for this layer in the declaration. Finally background-color is set to the specified color, if any, else set to its initial value.
If one
<box>
value is present then it sets both background-origin and background-clip to that value. If two values are present, then the first sets background-origin and the second background-clip.–––– CSS Backgrounds and Borders Module Level 3 - backgroundopen in new window
顺序并非固定, 但是要注意:
background-position
和background-size
属性,之间需使用/
分隔,且background-position
值在前,background-size
值在后。- 如果同时使用
background-origin
和background-clip
属性,origin
属性值需在clip
属性值之前, 如果origin
与clip
属性值相同, 则可只设置一个值。
需要注意的是,对于 CSS 预处理器来说,当在缩写里同时使用background-position
和background-size
时,中间的/
会被当成除号对待,待找出解决办法。
animation
animation
简写顺序:
<single-animation> =
<time> ||
<timing-function> ||
<time> ||
<single-animation-iteration-count> ||
<single-animation-direction> ||
<single-animation-fill-mode> ||
<single-animation-play-state> ||
[ none | <keyframes-name> ]
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Note that order is important within each animation definition: the first value in each
<animation>
that can be parsed as a<time>
is assigned to theanimation-duration
, and the second value in each<animation>
that can be parsed as a<time>
is assigned toanimation-delay
.Note that order is also important within each animation definition for distinguishing
<keyframes-name>
values from other keywords. When parsing, keywords that are valid for properties other than animation-name whose values were not found earlier in the shorthand must be accepted for those properties rather than for animation-name. Furthermore, when serializing, default values of other properties must be output in at least the cases necessary to distinguish an animation-name that could be a value of another property, and may be output in additional cases.
其他
- 类似
margin
/padding
这类具有四个值的属性,书写顺序是:上、右、下、左