> 參考：
http://alloyteam.github.io/CodeGuide/ (騰訊前端代碼規范)
http://www.waylau.com/css-code-guide/
[TOC]
# 縮進
使用 soft tab（4個空格）。
~~~
.element {
position: absolute;
top: 10px;
left: 10px;
border-radius: 10px;
width: 50px;
height: 50px;
}
~~~
# 分號
每個屬性聲明末尾都要加分號。
~~~
.element {
width: 20px;
height: 20px;
background-color: red;
}
~~~
# 空格
* 以下幾種情況不需要空格：
? 屬性名后
? 多個規則的分隔符`,`前
? !important `!`后
? 屬性值中`(`后和`)`前
? 行末不要有多余的空格
* 以下幾種情況需要空格：
? 屬性值前
? 選擇器`>`, `+`,`` ~``前后
? `{`前
? !important `!`前
? `@else` 前后
? 屬性值中的`,`后
? 注釋``/*后和`*/`前
~~~
/* not good */
.element {
color :red! important;
background-color: rgba(0,0,0,.5);
}
/* good */
.element {
color: red !important;
background-color: rgba(0, 0, 0, .5);
}
/* not good */
.element ,
.dialog{
...
}
/* good */
.element,
.dialog {
}
/* not good */
.element>.dialog{
...
}
/* good */
.element > .dialog{
...
}
/* not good */
.element{
...
}
/* good */
.element {
...
}
/* not good */
@if{
...
}@else{
...
}
/* good */
@if {
...
} @else {
...
}
~~~
# 空行
* 以下幾種情況需要空行：
? 文件最后保留一個空行
? `}`后最好跟一個空行，包括scss中嵌套的規則
? 屬性之間需要適當的空行，具體見屬性聲明順序
~~~
/* not good */
.element {
...
}
.dialog {
color: red;
&:after {
...
}
}
/* good */
.element {
...
}
.dialog {
color: red;
&:after {
...
}
}
~~~
# 換行
* 以下幾種情況不需要換行：
? {`前
* 以下幾種情況需要換行：
? `{`后和`}`前
? 每個屬性獨占一行
? 多個規則的分隔符`,`后
~~~
/* not good */
.element
{color: red; background-color: black;}
/* good */
.element {
color: red;
background-color: black;
}
/* not good */
.element, .dialog {
...
}
/* good */
.element,
.dialog {
...
}
~~~
# 注釋
* 注釋統一用`/* */`（scss中也不要用`//`），具體參照例子的寫法；
* 縮進與下一行代碼保持一致；
* 可位于一個代碼行的末尾，與代碼間隔一個空格。
~~~
/* Modal header */
.modal-header {
...
}
/*
* Modal header
*/
.modal-header {
...
}
.modal-header {
/* 50px */
width: 50px;
color: red; /* color red */
}
~~~
# 引號
* 最外層統一使用雙引號；
* url的內容要用引號；
* 屬性選擇器中的屬性值需要引號。
~~~
.element:after {
content: "";
background-image: url("logo.png");
}
li[data-type="single"] {
...
}
~~~
# 命名
* css 元素名稱以及id和類名的命名也是**區分大小寫**的（但是屬性和值不區分）
* 類名使用小寫字母，以中劃線`-`分隔
* id采用駝峰式命名
* scss中的變量、函數、混合、placeholder采用駝峰式命名
~~~
/* class */
.element-content {
...
}
/* id */
#myDialog {
...
}
/* 變量 */
$colorBlack: #000;
/* 函數 */
@function pxToRem($px) {
...
}
/* 混合 */
@mixin centerBlock {
...
}
/* placeholder */
%myDialog {
...
}
~~~
# 屬性聲明順序
* 相關的屬性聲明按例子的順序做分組處理，組之間需要有一個空行。
~~~
.declaration-order {
display: block;
float: right;
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
z-index: 100;
border: 1px solid #e5e5e5;
border-radius: 3px;
width: 100px;
height: 100px;
font: normal 13px "Helvetica Neue", sans-serif;
line-height: 1.5;
text-align: center;
color: #333;
background-color: #f5f5f5;
opacity: 1;
}
// 下面是推薦的屬性的順序
[
[
"display",
"visibility",
"float",
"clear",
"overflow",
"overflow-x",
"overflow-y",
"clip",
"zoom"
],
[
"table-layout",
"empty-cells",
"caption-side",
"border-spacing",
"border-collapse",
"list-style",
"list-style-position",
"list-style-type",
"list-style-image"
],
[
"-webkit-box-orient",
"-webkit-box-direction",
"-webkit-box-decoration-break",
"-webkit-box-pack",
"-webkit-box-align",
"-webkit-box-flex"
],
[
"position",
"top",
"right",
"bottom",
"left",
"z-index"
],
[
"margin",
"margin-top",
"margin-right",
"margin-bottom",
"margin-left",
"-webkit-box-sizing",
"-moz-box-sizing",
"box-sizing",
"border",
"border-width",
"border-style",
"border-color",
"border-top",
"border-top-width",
"border-top-style",
"border-top-color",
"border-right",
"border-right-width",
"border-right-style",
"border-right-color",
"border-bottom",
"border-bottom-width",
"border-bottom-style",
"border-bottom-color",
"border-left",
"border-left-width",
"border-left-style",
"border-left-color",
"-webkit-border-radius",
"-moz-border-radius",
"border-radius",
"-webkit-border-top-left-radius",
"-moz-border-radius-topleft",
"border-top-left-radius",
"-webkit-border-top-right-radius",
"-moz-border-radius-topright",
"border-top-right-radius",
"-webkit-border-bottom-right-radius",
"-moz-border-radius-bottomright",
"border-bottom-right-radius",
"-webkit-border-bottom-left-radius",
"-moz-border-radius-bottomleft",
"border-bottom-left-radius",
"-webkit-border-image",
"-moz-border-image",
"-o-border-image",
"border-image",
"-webkit-border-image-source",
"-moz-border-image-source",
"-o-border-image-source",
"border-image-source",
"-webkit-border-image-slice",
"-moz-border-image-slice",
"-o-border-image-slice",
"border-image-slice",
"-webkit-border-image-width",
"-moz-border-image-width",
"-o-border-image-width",
"border-image-width",
"-webkit-border-image-outset",
"-moz-border-image-outset",
"-o-border-image-outset",
"border-image-outset",
"-webkit-border-image-repeat",
"-moz-border-image-repeat",
"-o-border-image-repeat",
"border-image-repeat",
"padding",
"padding-top",
"padding-right",
"padding-bottom",
"padding-left",
"width",
"min-width",
"max-width",
"height",
"min-height",
"max-height"
],
[
"font",
"font-family",
"font-size",
"font-weight",
"font-style",
"font-variant",
"font-size-adjust",
"font-stretch",
"font-effect",
"font-emphasize",
"font-emphasize-position",
"font-emphasize-style",
"font-smooth",
"line-height",
"text-align",
"-webkit-text-align-last",
"-moz-text-align-last",
"-ms-text-align-last",
"text-align-last",
"vertical-align",
"white-space",
"text-decoration",
"text-emphasis",
"text-emphasis-color",
"text-emphasis-style",
"text-emphasis-position",
"text-indent",
"-ms-text-justify",
"text-justify",
"letter-spacing",
"word-spacing",
"-ms-writing-mode",
"text-outline",
"text-transform",
"text-wrap",
"-ms-text-overflow",
"text-overflow",
"text-overflow-ellipsis",
"text-overflow-mode",
"-ms-word-wrap",
"word-wrap",
"-ms-word-break",
"word-break"
],
[
"color",
"background",
"filter:progid:DXImageTransform.Microsoft.AlphaImageLoader",
"background-color",
"background-image",
"background-repeat",
"background-attachment",
"background-position",
"-ms-background-position-x",
"background-position-x",
"-ms-background-position-y",
"background-position-y",
"-webkit-background-clip",
"-moz-background-clip",
"background-clip",
"background-origin",
"-webkit-background-size",
"-moz-background-size",
"-o-background-size",
"background-size"
],
[
"outline",
"outline-width",
"outline-style",
"outline-color",
"outline-offset",
"opacity",
"filter:progid:DXImageTransform.Microsoft.Alpha(Opacity",
"-ms-filter:\\'progid:DXImageTransform.Microsoft.Alpha",
"-ms-interpolation-mode",
"-webkit-box-shadow",
"-moz-box-shadow",
"box-shadow",
"filter:progid:DXImageTransform.Microsoft.gradient",
"-ms-filter:\\'progid:DXImageTransform.Microsoft.gradient",
"text-shadow"
],
[
"-webkit-transition",
"-moz-transition",
"-ms-transition",
"-o-transition",
"transition",
"-webkit-transition-delay",
"-moz-transition-delay",
"-ms-transition-delay",
"-o-transition-delay",
"transition-delay",
"-webkit-transition-timing-function",
"-moz-transition-timing-function",
"-ms-transition-timing-function",
"-o-transition-timing-function",
"transition-timing-function",
"-webkit-transition-duration",
"-moz-transition-duration",
"-ms-transition-duration",
"-o-transition-duration",
"transition-duration",
"-webkit-transition-property",
"-moz-transition-property",
"-ms-transition-property",
"-o-transition-property",
"transition-property",
"-webkit-transform",
"-moz-transform",
"-ms-transform",
"-o-transform",
"transform",
"-webkit-transform-origin",
"-moz-transform-origin",
"-ms-transform-origin",
"-o-transform-origin",
"transform-origin",
"-webkit-animation",
"-moz-animation",
"-ms-animation",
"-o-animation",
"animation",
"-webkit-animation-name",
"-moz-animation-name",
"-ms-animation-name",
"-o-animation-name",
"animation-name",
"-webkit-animation-duration",
"-moz-animation-duration",
"-ms-animation-duration",
"-o-animation-duration",
"animation-duration",
"-webkit-animation-play-state",
"-moz-animation-play-state",
"-ms-animation-play-state",
"-o-animation-play-state",
"animation-play-state",
"-webkit-animation-timing-function",
"-moz-animation-timing-function",
"-ms-animation-timing-function",
"-o-animation-timing-function",
"animation-timing-function",
"-webkit-animation-delay",
"-moz-animation-delay",
"-ms-animation-delay",
"-o-animation-delay",
"animation-delay",
"-webkit-animation-iteration-count",
"-moz-animation-iteration-count",
"-ms-animation-iteration-count",
"-o-animation-iteration-count",
"animation-iteration-count",
"-webkit-animation-direction",
"-moz-animation-direction",
"-ms-animation-direction",
"-o-animation-direction",
"animation-direction"
],
[
"content",
"quotes",
"counter-reset",
"counter-increment",
"resize",
"cursor",
"-webkit-user-select",
"-moz-user-select",
"-ms-user-select",
"user-select",
"nav-index",
"nav-up",
"nav-right",
"nav-down",
"nav-left",
"-moz-tab-size",
"-o-tab-size",
"tab-size",
"-webkit-hyphens",
"-moz-hyphens",
"hyphens",
"pointer-events"
]
]
~~~
# 顏色
* 使顏色16進制用小寫字母；
* 顏色16進制盡量用簡寫。
~~~
/* not good */
.element {
color: #ABCDEF;
background-color: #001122;
}
/* good */
.element {
color: #abcdef;
background-color: #012;
}
~~~
# 屬性簡寫
* 屬性簡寫需要你非常清楚屬性值的正確順序，而且在大多數情況下并不需要設置屬性簡寫中包含的所有值，所以建議盡量分開聲明會更加清晰；
* margin 和 padding 相反，需要使用簡寫；
* 常見的屬性簡寫包括：
? font
? background
? transition
? animation
~~~
/* not good */
.element {
transition: opacity 1s linear 2s;
}
/* good */
.element {
transition-delay: 2s;
transition-timing-function: linear;
transition-duration: 1s;
transition-property: opacity;
}
~~~
# 媒體查詢
**盡量將媒體查詢的規則被包含在他們相關的規則**，不要將他們一起放到一個獨立的樣式文件中，或者丟在文檔的最底部，這樣做只會讓大家以后更容易忘記他們。
```css
// Example:
button {
font-size: 0.875rem;
// All the internal/external value use in 'em'
// This value use of your "font-size" as the basic font size
// And you will not have any problem with the font size of the container ( Example bottom )
padding: .5em 1em;
border: .125em solid #e3e3e3;
@media (min-width: 48rem){ // min-width: 768px
font-size: 1.125rem;
}
@media (min-width: 62rem){ // min-width: 992px
font-size: 1.375rem;
}
}
```
# 雜項
* 不允許有空的規則；
* 元素選擇器用小寫字母；
* **去掉小數點前面的0；**
* 去掉數字中不必要的小數點和末尾的0；
* **屬性值`0`后面不要加單位；**
* 禁止使用`expression`表達式；
* 禁止濫用`!important`；
* 同個屬性不同前綴的寫法需要在垂直方向保持對齊，具體參照右邊的寫法；
* 無前綴的標準屬性應該寫在有前綴的屬性后面；
~~~
-ms-transform:rotate(7deg); //-ms代表ie內核識別碼
-moz-transform:rotate(7deg); //-moz代表火狐內核識別碼
-webkit-transform:rotate(7deg); //-webkit代表谷歌內核識別碼
-o-transform:rotate(7deg); //Opera15以前加 -o-，Opera15及以后加 -webkit-。
transform:rotate(7deg); //統一標識語句,符合w3c標準
~~~
* 不要在同個規則里出現重復的屬性，如果重復的屬性是連續的則沒關系；
* 不要在一個文件里出現兩個相同的規則；
* 用 `border: 0;` 代替 `border: none;`；
* 在保證選擇器準確的情況下盡量簡化選擇器 (盡量不超過4級，最多4級)，不寫多余的選擇器(如class/id前的標簽選擇器、li上一級的的ul/ol、dt/dd上一級的dl等，在保證準確的前提下能去掉的都去掉)（在`scss`中如果超過4層應該考慮用嵌套的方式來寫）；
* **盡量少用`*`選擇器。**
~~~
/* not good */
.element {
}
/* not good */
LI {
...
}
/* good */
li {
...
}
/* not good */
.element {
color: rgba(0, 0, 0, 0.5);
}
/* good */
.element {
color: rgba(0, 0, 0, .5);
}
/* not good */
.element {
width: 50.0px;
}
/* good */
.element {
width: 50px;
}
/* not good */
.element {
width: 0px;
}
/* good */
.element {
width: 0;
}
/* not good */
.element {
border-radius: 3px;
-webkit-border-radius: 3px;
-moz-border-radius: 3px;
background: linear-gradient(to bottom, #fff 0, #eee 100%);
background: -webkit-linear-gradient(top, #fff 0, #eee 100%);
background: -moz-linear-gradient(top, #fff 0, #eee 100%);
}
/* good */
.element {
-webkit-border-radius: 3px;
-moz-border-radius: 3px;
border-radius: 3px;
background: -webkit-linear-gradient(top, #fff 0, #eee 100%);
background: -moz-linear-gradient(top, #fff 0, #eee 100%);
background: linear-gradient(to bottom, #fff 0, #eee 100%);
}
/* not good */
.element {
color: rgb(0, 0, 0);
width: 50px;
color: rgba(0, 0, 0, .5);
}
/* good */
.element {
color: rgb(0, 0, 0);
color: rgba(0, 0, 0, .5);
}
~~~
* 避免使用 @import語句。如果使用了@import語句，一定要將它們寫在樣式表開頭，保證它的優先級低于樣式表中的其他規則；與 `<link>` 標簽相比，`@import` 指令要慢很多，不光增加了額外的請求次數，還會導致不可預料的問題。替代辦法有以下幾種：
? 使用多個 `<link>` 元素
? 通過 Sass 或 Less 類似的 CSS 預處理器將多個 CSS 文件編譯為一個文件
? 通過 Rails、Jekyll 或其他系統中提供過 CSS 文件合并功能
? 請參考 http://www.stevesouders.com/blog/2009/04/09/dont-use-import/ 了解更多知識。
```html
<!-- Use link elements -->
<link rel="stylesheet" href="core.css">
<!-- Avoid @imports -->
<style>
@import url("more.css");
</style>
```
