CSS 规范
目录
缩进
-
使用 soft tab（4个空格）。
.element { position: absolute; top: 10px; left: 10px; border-radius: 10px; width: 50px; height: 50px; }
分号
-
每个属性声明末尾都要加分号。
.element { width: 20px; height: 20px; background-color: red; }
空格
- 以下几种情况不需要空格：
- 属性名后
- 多个规则的分隔符
,前 - !important
!后 - 属性值中
(后和)前 - 行末不要有多余的空格
- 以下几种情况需要空格：
- 属性值前
- 选择器
>,+,~前后 {前- !important
!前 @else前后- 属性值中的
,后 - 注释
/*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
- 以下几种情况需要空行：
- 文件最后保留一个空行
}后最好跟一个空行，包括scss中嵌套的规则- 属性之间需要适当的空行，具体见属性声明顺序
/* not good */ .element { ... } .dialog { color: red; &:after { ... } } /* good */ .element { ... } .dialog { color: red; &:after { ... } }
换行
- 以下几种情况不需要换行：
{前
- 以下几种情况需要换行：
{后和}前- 每个属性独占一行
- 多个规则的分隔符
,后
/* not good */ .element {color: red; background-color: black;} /* good */ .element { color: red; background-color: black; } /* not good */ .element, .dialog { ... } /* good */ .element, .dialog { ... }
注释
- 注释统一用
/* */（scss中也不要用//），具体参照例子的写法； - 缩进与下一行代码保持一致；
-
可位于一个代码行的末尾，与代码间隔一个空格。
/* Modal header */ .modal-header { ... } /* * Modal header */ .modal-header { ... } .modal-header { /* 50px */ width: 50px; color: red; /* color red */ }
引号
- 最外层统一使用双引号；
- url的内容要用引号；
-
属性选择器中的属性值需要引号。
.element:after { content: ""; background-image: url("logo.png"); } li[data-type="single"] { ... }
命名
- 类名使用小写字母，以中划线分隔
- id采用驼峰式命名
-
scss中的变量、函数、混合、placeholder采用驼峰式命名
/* class */ .element-content { ... } /* id */ #myDialog { ... } /* 变量 */ $colorBlack: #000; /* 函数 */ @function pxToRem($px) { ... } /* 混合 */ @mixin centerBlock { ... } /* placeholder */ %myDialog { ... }
属性声明顺序
-
相关的属性声明按例子的顺序做分组处理，组之间需要有一个空行。
.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; } // 下面是推荐的属性的顺序 [ [ "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" ] ]
颜色
- 使颜色16进制用小写字母；
-
颜色16进制尽量用简写。
/* not good */ .element { color: #ABCDEF; background-color: #001122; } /* good */ .element { color: #abcdef; background-color: #012; }
属性简写
- 属性简写需要你非常清楚属性值的正确顺序，而且在大多数情况下并不需要设置属性简写中包含的所有值，所以建议尽量分开声明会更加清晰；
margin和padding相反，需要使用简写；- 常见的属性简写包括：
fontbackgroundtransitionanimation
/* not good */ .element { transition: opacity 1s linear 2s; } /* good */ .element { transition-delay: 2s; transition-timing-function: linear; transition-duration: 1s; transition-property: opacity; }
媒体查询
-
尽量将媒体查询的规则靠近与他们相关的规则，不要将他们一起放到一个独立的样式文件中，或者丢在文档的最底部，这样做只会让大家以后更容易忘记他们。
.element { ... } .element-avatar{ ... } @media (min-width: 480px) { .element { ... } .element-avatar { ... } }
杂项
- 不允许有空的规则；
- 元素选择器用小写字母；
- 去掉小数点前面的0；
- 去掉数字中不必要的小数点和末尾的0；
- 属性值
0后面不要加单位； - 同个属性不同前缀的写法需要在垂直方向保持对齐，具体参照右边的写法；
- 无前缀的标准属性应该写在有前缀的属性后面；
- 不要在同个规则里出现重复的属性，如果重复的属性是连续的则没关系；
- 不要在一个文件里出现两个相同的规则；
- 用
border: 0;代替border: none;； - 选择器不要超过4层（在scss中如果超过4层应该考虑用嵌套的方式来写）；
-
尽量少用
*选择器。/* 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); } - 不要使用有
@import；与<link>标签相比，@import指令要慢很多，不光增加了额外的请求次数，还会导致不可预料的问题。替代办法有以下几种：- 使用多个
<link>元素 - 通过 Sass 或 Less 类似的 CSS 预处理器将多个 CSS 文件编译为一个文件
- 通过 Rails、Jekyll 或其他系统中提供过 CSS 文件合并功能
- 请参考 http://www.stevesouders.com/blog/2009/04/09/dont-use-import/ 了解更多知识。
<!-- Use link elements --> <link rel="stylesheet" href="core.css"> <!-- Avoid @imports --> <style> @import url("more.css"); </style> - 使用多个
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