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<span style="color: #008080;"> 1</span> <span style="color: #000000;">使用 @ 定义变量
</span><span style="color: #008080;"> 2</span> <span style="color: #000000;">    变量可以做运算
</span><span style="color: #008080;"> 3</span>     
<span style="color: #008080;"> 4</span> <span style="color: #000000;">    @color : #000;
</span><span style="color: #008080;"> 5</span> <span style="color: #000000;">    @width : 1000px;
</span><span style="color: #008080;"> 6</span>     
<span style="color: #008080;"> 7</span> <span style="color: #000000;">使用 & 表示当前类
</span><span style="color: #008080;"> 8</span> <span style="color: #000000;">    .box{
</span><span style="color: #008080;"> 9</span> <span style="color: #000000;">        &:hover{
</span><span style="color: #008080;">10</span> <span style="color: #000000;">            color : #000;
</span><span style="color: #008080;">11</span> <span style="color: #000000;">        }
</span><span style="color: #008080;">12</span> <span style="color: #000000;">    }
</span><span style="color: #008080;">13</span> 
<span style="color: #008080;">14</span> <span style="color: #000000;">css 可以嵌套
</span><span style="color: #008080;">15</span> 
<span style="color: #008080;">16</span> <span style="color: #000000;">    ul{
</span><span style="color: #008080;">17</span> <span style="color: #000000;">        display : block;
</span><span style="color: #008080;">18</span> <span style="color: #000000;">        li{
</span><span style="color: #008080;">19</span> <span style="color: #000000;">            float : left;
</span><span style="color: #008080;">20</span> <span style="color: #000000;">            a{
</span><span style="color: #008080;">21</span> <span style="color: #000000;">                font-size : 18px;
</span><span style="color: #008080;">22</span> <span style="color: #000000;">            }
</span><span style="color: #008080;">23</span> <span style="color: #000000;">        }
</span><span style="color: #008080;">24</span> <span style="color: #000000;">    }
</span><span style="color: #008080;">25</span> 
<span style="color: #008080;">26</span> <span style="color: #000000;">继承 ： 直接在需要的地方引用 class或者 id 类
</span><span style="color: #008080;">27</span> 
<span style="color: #008080;">28</span> <span style="color: #000000;">.clearfix{
</span><span style="color: #008080;">29</span> <span style="color: #000000;">    zoom : 1;
</span><span style="color: #008080;">30</span> <span style="color: #000000;">    display : block;
</span><span style="color: #008080;">31</span> <span style="color: #000000;">    &:after{
</span><span style="color: #008080;">32</span> <span style="color: #000000;">        content: "";
</span><span style="color: #008080;">33</span> <span style="color: #000000;">        visibility: hidden;
</span><span style="color: #008080;">34</span> <span style="color: #000000;">        clear: both;
</span><span style="color: #008080;">35</span> <span style="color: #000000;">        height: 0;
</span><span style="color: #008080;">36</span> <span style="color: #000000;">        display: block;
</span><span style="color: #008080;">37</span> <span style="color: #000000;">    }
</span><span style="color: #008080;">38</span> <span style="color: #000000;">}
</span><span style="color: #008080;">39</span> 
<span style="color: #008080;">40</span> <span style="color: #000000;">.radius(@radius : 15px){
</span><span style="color: #008080;">41</span> <span style="color: #000000;">    border-radius: @radius;
</span><span style="color: #008080;">42</span> <span style="color: #000000;">}
</span><span style="color: #008080;">43</span> 
<span style="color: #008080;">44</span> <span style="color: #000000;">.box{
</span><span style="color: #008080;">45</span> <span style="color: #000000;">    .clearfix;
</span><span style="color: #008080;">46</span> <span style="color: #000000;">    .radius(10px);
</span><span style="color: #008080;">47</span> <span style="color: #000000;">}
</span><span style="color: #008080;">48</span> 
<span style="color: #008080;">49</span> <span style="color: #000000;">混合 ： 类似 js 中的函数, [或者叫继承]
</span><span style="color: #008080;">50</span> <span style="color: #000000;">.layout(){
</span><span style="color: #008080;">51</span> <span style="color: #000000;">    ...
</span><span style="color: #008080;">52</span> <span style="color: #000000;">}
</span><span style="color: #008080;">53</span> 
<span style="color: #008080;">54</span> 
<span style="color: #008080;">55</span> <span style="color: #000000;">作用域 ： 限制继承的条件，可以继承一个 类的部分内容
</span><span style="color: #008080;">56</span> 
<span style="color: #008080;">57</span> <span style="color: #000000;">延伸 ： &:extend(.box); 括号中可以填写多个 类名  编译后的效果就是 css 中的分组
</span><span style="color: #008080;">58</span> 
<span style="color: #008080;">59</span> 
<span style="color: #008080;">60</span> <span style="color: #000000;">when 用来做条件判断
</span><span style="color: #008080;">61</span> 
<span style="color: #008080;">62</span> <span style="color: #000000;">when not 不等于
</span><span style="color: #008080;">63</span> 
<span style="color: #008080;">64</span> <span style="color: #000000;">/*
</span><span style="color: #008080;">65</span> <span style="color: #000000;">    使用 isnumber 来判断某个参数是否为 数字
</span><span style="color: #008080;">66</span> <span style="color: #000000;"> * */
</span><span style="color: #008080;">67</span> 
<span style="color: #008080;">68</span> <span style="color: #000000;">.border(@width : 1px , @style : solid, @color : #d1d1d1) when (isnumber(@width)){
</span><span style="color: #008080;">69</span> <span style="color: #000000;">    border: @width @style @color;
</span><span style="color: #008080;">70</span> <span style="color: #000000;">}
</span><span style="color: #008080;">71</span> 
<span style="color: #008080;">72</span> <span style="color: #000000;">/*
</span><span style="color: #008080;">73</span> <span style="color: #000000;">    使用 iscolor 来判断某个参数是否为 颜色
</span><span style="color: #008080;">74</span> <span style="color: #000000;"> * */
</span><span style="color: #008080;">75</span> 
<span style="color: #008080;">76</span> <span style="color: #000000;">.border(@color) when (iscolor(@color)){
</span><span style="color: #008080;">77</span>     
<span style="color: #008080;">78</span> <span style="color: #000000;">    .border(1px , solid , @color);
</span><span style="color: #008080;">79</span> <span style="color: #000000;">}
</span><span style="color: #008080;">80</span> 
<span style="color: #008080;">81</span> 
<span style="color: #008080;">82</span> <span style="color: #000000;">.border(@solid) when not ( iscolor(@solid)) , ( isnumber(@solid) ){
</span><span style="color: #008080;">83</span> <span style="color: #000000;">    .border(1px , @solid);
</span><span style="color: #008080;">84</span> }

Use @ to define variables. Variables can perform operations @color: #000;@width: 1000px; use & to represent the current class.box{&:hover{color: #000;}}
css can be nested
ul{display: block ;li{float : left;a{font-size : 18px;}}}
Inheritance: directly reference the class or id class where needed
.clearfix{zoom : 1;display : block;&:after{content: " "; visibility: hidden; clear: both; height: 0; display: block;}}
.radius(@radius : 15px){border-radius: @radius;}
.box{.clearfix;.radius(10px) ;}
Mixing: Similar to functions in js, [or inheritance].layout(){...}

Scope: Restrict the conditions for inheritance, you can inherit part of a class
Extension: &:extend(. box); Multiple class names can be filled in the brackets. The compiled effect is the grouping in CSS

when is used to make conditional judgments
when not not equal to
/* Use isnumber to determine whether a parameter is a number * */
.border(@width : 1px , @style : solid, @color : #d1d1d1) when (isnumber(@width)){ border: @width @style @color;}
/* Use iscolor to determine whether a parameter is Color * */
.border(@color) when (iscolor(@color)){ .border(1px , solid , @color);}

.border(@solid) when not ( iscolor(@solid)) , ( isnumber(@solid) ){ .border(1px , @solid);}