First use of SASS

This time I will bring you the first use of SASS. What are the precautions when using SASS for the first time. The following is a practical case, let’s take a look.

First experience with SASS

Tags (separated by spaces): sass scss css

---

1. Compilation environment
Requires Ruby to be installed, After that, you need to open Start Command Prompt with Ruby to run

gem install sass

2. Command line compilation

sass /style.scss:/style.css

Multiple file compilation (must use - -watch? Anyway, I will report an error if I don’t add watch)

sass --watch sass/:css/

Enable watch

sass --watch /style.scss:/style.css

Output method--style [nested (the last curly bracket does not wrap)|expanded (fully expanded)|compact(single line)|compressed(compressed)]

sass --watch sass/:css/ --style compressed

3. Basic syntax

(1). Nesting

is almost the same as less.

nav {
    color: blue;
    li {
        color: yellow;
        a {
            color: red;
            header & {
                color: green;
            }
        }
    }
}

After compilation

nav {
  color: blue;
}
nav li {
  color: yellow;
}
nav li a {
  color: red;
}
header nav li a {
  color: green;
}

• Attributes are nested (same attribute prefix), and attributes can be added after the prefix colon

.box {
    font: 12px/24px {
        size: 12px;
        weight: bold;
    }
}

After compilation

.box { font: 12px/24px; font-size: 12px; font-weight: bold; }

• Pseudo class nesting, the same as less

.clearfix {
    &:before,
    &:after {
        content: "";
        display: table;
    }
    &:after {
        clear: both;
        overflow: hidden;
    }
}

After compilation

.clearfix:before, .clearfix:after {
  content: "";
  display: table;
}
.clearfix:after {
  clear: both;
  overflow: hidden;
}

• Parent selector& can be used as the first character of the selector, such as

.btn {
    padding: 4px 12px;
    font-size: 16px;
    border: 1px solid #ddd;
    color: #333;
    &-primary {
        border-color: #ff5f00;
        background: #ff5f00;
        color: #fff;
    }
}

after compilation

.btn, .btn-primary { padding: 4px 12px; font-size: 16px; border: 1px solid #ddd; color: #333; }
.btn-primary { border-color: #ff5f00; background: #ff5f00; color: #fff; }

(2). The comment

/**/ will appear in the compiled file amazing!
// will not

// 方向
/*方向*/
$d: "right";
.box {
    @extend %border-#{$d};
}
/*位置*/

After compilation

.box {
  border-right: 2px solid #ddd;
}
/*方向*/
/*位置*/

---

(3). Variable

##$[Variable name]: [Value] Block-level scope

!globalDeclaration can convert local variables into global variablesDefault variables; ordinary variables will overwrite default variables

$size: 16px;
$size: 14px !default;
p.p-1 {
    font-size: $size;
}

After compilation

p.p-1 {font-size:16px}

(4). Operation

+, -, *, /, %
, = can also be used for numerical operations==, != can be used for all data types Operations cannot be performed on different units
String concatenation can be performed; and whether or not there are quotation marks is determined by the left side
Division needs to be in a mathematical expression, and two common attributes need to be enclosed in parentheses, such as

.box {
    width: (100px / 2);
}

After compilation

.box {
  width: 50px;
}

• The variables wrapped in the interpolation statement do not perform division operations

p {
    $font-size: 12px;
    $line-height: 30px;
    font: #{$font-size}/#{$line-height};
}

After compilation

p { font: 12px/30px; }

• Color calculation segmentation (according to red, green and blue)

  Color function
  Among them,
  fade-in($color, $amount) and other methods, the color parameter can only be rgba()Color, different from less

##(5). Mix

Used to define reusable styles. Note that the syntax does not include dots, and the default parameter values ​​are the same as less.

• @mixin [mixin-name]([$param1, $param2: default-value ]) { ... }
  Use: @include [mixin-name](value1, value2);
  

For indefinite parameters, Use
• ...

  , such as

  @mixin box-shadow($shadows...) { 
      -moz-box-shadow: $shadows; 
      -webkit-box-shadow: $shadows; 
      box-shadow: $shadows; 
  }

(6). Inherit

• @extend .[class]

You can also inherit any selector defined for a single element, such as
• @extend a:hover;

  .btn {
      border: 1px solid #999;
      padding: 4px 12px;
      font-size: 14px;
      background: #ddd;
      color: #333;
  }
  .btn-primary {
      background: #ff5f00;
      color: #fff;
      @extend .btn;
  }

After compilation

.btn, .btn-primary {
  border: 1px solid #999;
  padding: 4px 12px;
  font-size: 14px;
  background: #ddd;
  color: #333;
}
.btn-primary {
  background: #ff5f00;
  color: #fff;
}

Placeholder

%

Code declared with placeholders is not @extend
The call will not be compiled The same style will be combined through ,
to reduce the amount of code <pre class="brush:php;toolbar:false">%box-padding {     padding: 4px 12px; } .box {     font-size: 14px;     @extend %box-padding; } .box-2 {     font-size: 18px;     @extend %box-padding; }</pre>After compilation

.box, .box-2 {
  padding: 4px 12px;
}
.box {
  font-size: 14px;
}
.box-2 {
  font-size: 18px;
}

(7) . Interpolation

Variables can be used in selectors or attribute names through the

#{}

interpolation statement#{$[param]}
Usage , can be used in @each, @extend, multi-line comments <pre class="brush:php;toolbar:false">$border-properties: (border); @mixin set-border($direction, $val) {     @each $prop in $border-properties {         #{$prop}-#{$direction}: $val;     } } .box {     @include set-border(left, 1px solid #ddd); }</pre>After compilation

.box {
  border-left: 1px solid #ddd;
}

%border-right {
    border-right: 2px solid #ddd;
}
$d: "right";
.box {
    @extend %border-#{$d};
}

After compilation

.box {
  border-right: 2px solid #ddd;
}

(8). 导入

• @import可以导入多个文件，比如@import "rounded-corners", "text-shadow";

• 导入文件可以通过url()的方式使用插值语句#{}，比如@import url("http://fonts.googleapis.com/css?family=\#{$family}");

• 如果想使一个sass文件只作为导入文件，不进行编译，在文件名前加_即可，比如文件命名为_colors.scss，使用@import "colors";导入，注意文件夹下不能再有colors.scss文件。

• 可以用在嵌套中，作用域就只在当前嵌套中了，很赞；但是不可以在混合指令 (mixin) 或控制指令 (control directives) 中嵌套 @import。

(9). 媒体查询 @media

• 用法同css

• 可以写在嵌套中，编译后将会编译在最外层，且里面的选择器会是嵌套时候的选择器
  比如

.sidebar {
    width: 300px;
    @media screen and (orientation: landscape) {
        width: 500px;
    }
}

.sidebar { width: 300px; }
@media screen and (orientation: landscape) { .sidebar { width: 500px; } }

• media的查询条件可以使用插值语句

• media的查询条件可以嵌套

(10). @at-root

• 将嵌套的选择器提升到当前文档最顶层， 比如

.parent {
    font-size: 14px;
    @at-root .child-a {
        font-size: 16px;
        @at-root .child-c {
            font-size: 18px;
        }
    }
    .child-b {
        font-size: 12px;
    }
}

.parent { font-size: 14px; }
.child-a { font-size: 16px; }
.child-c { font-size: 18px; }
.parent .child-b { font-size: 12px; }

• @at-root (without: [directive1 directive2 ...])可以排除前面的指令

• 括号后面不能有选择器，没有括号必须有选择器

@media .print {
    .page {
        width: 8in;
        @at-root (without: media) {
            color: red;
        }
    }
}
// 没有without
@media print {
    .page {
        width: 8in;
        @at-root .p {
            color: red;
        }
    }
}

@media .print { .page { width: 8in; } }
.page { color: red; }
@media print { .page { width: 8in; }
  .p { color: red; } }

(11). 控制指令

• 主要与混合指令 (mixin) 配合使用,
  这是less中所没有的，less通过其它方式可以实现类似的效果，比如循环，less可以通过递归配合when关键字来实现：.loop(@counter) when (@counter > 0) { .loop((@counter - 1)); }

• @if 表达式返回值不是 false 或者 null 时，执行 {} 内的样式，同样还有@else if和@else

• @for 语法：@for $var from <start> through <end></end></start> 或者 @for $var from <start> to <end></end></start>
<start></start> 和 <end></end> 必须为整数
  through 包含 <start></start> 和 <end></end> 的值，而 to 只包含 <start></start>

• @each 语法： $var in <list></list>
<list></list> 值为列表
  比如

$arr: a, b, c, d, e;
@each $img in $arr {
    .box-#{$img} {
        background: url('/img/#{$img}.png') no-repeat;
    }
}

.box-a { background: url("/img/a.png") no-repeat; }
.box-b { background: url("/img/b.png") no-repeat; }
.box-c { background: url("/img/c.png") no-repeat; }
.box-d { background: url("/img/d.png") no-repeat; }
.box-e { background: url("/img/e.png") no-repeat; }

• 可以循环多维数组，比如

$list: (aa, pen), (bb, apple), (cc, bag);
@each $var, $img in $list {
    .box-#{$var} {
        background: url('/img/#{$img}.png') no-repeat;
    }
}

.box-aa { background: url("/img/pen.png") no-repeat; }
.box-bb { background: url("/img/apple.png") no-repeat; }
.box-cc { background: url("/img/bag.png") no-repeat; }

使用map数组或许更为明了：

$list-2: (aaa: yellow, bbb: blue, ccc: red);
@each $key, $color in $list-2 {
    .box-#{$key} {
        background: #{$color};
    }
}

.box-aaa { background: yellow; }
.box-bbb { background: blue; }
.box-ccc { background: red; }

• @while 循环，语法：@while [conditions] { ... }

(12). 其它

• @debug 可以输出信息到编译器

• @warn 将SassScript表达式的值打印到标准错误输出流。

• @error 抛出SassScript表达式的值作为致命错误

• @function 自定义函数

@function [function-name]([params]) {
    @return [value];
}

The end...    Last updated by: Jehorn, Mar 13, 2018, 12:10 PM

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