> For the complete documentation index, see [llms.txt](https://kasoqian.gitbook.io/code_standard/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kasoqian.gitbook.io/code_standard/programmer/css.md).

# css

## 缩进

使用soft tab（4个空格）。

```css
.element {
    position: absolute;
}
```

## 分号

每个属性声明末尾都要加分号。

```css
.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

```css
/* 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

```css
/* 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

```css
/* 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'//'），具体参照右边的写法；

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。

```css
/* 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。

```css
.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

```css
/* class */
.element-content {
    ...
}

/* id */
#myDialog {
    ...
}

/* 变量 */
$colorBlack: #000;

/* 函数 */
@function pxToRem($px) {
    ...
}

/* 混合 */
@mixin centerBlock {
    ...
}

/* placeholder */
%myDialog {
    ...
}
```

## 颜色

颜色16进制用小写字母；

颜色16进制尽量用简写。

```css
/* 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：

```css
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。

```css
.element {
    ...
}

.element-avatar{
    ...
}

@media (min-width: 480px) {
    .element {
        ...
    }

    .element-avatar {
        ...
    }
}
```

## 属性声明顺序

相关的属性声明按右边的顺序做分组处理，组之间需要有一个空行。

```css
.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;
}
```

```css
// 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"
    ]
]
```

## 参考源

1. [腾讯官方规范文档](http://alloyteam.github.io/CodeGuide/#css)


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