//扩展Extend

Use Method：以在study上扩展指定多层嵌套选择器样式

//Share style

.test{

    font-size:18px;

    color:#ffffff;

    ul{

        width:100px;

        height:50px;

        li{

            float:left;

            margin-right:10px;

            width:50px;

            height:50px;

        }

    }

}

//grammar 1

.study{

    &:extend(.test ul li);

}

//grammar 2

.study:extend(.test ul li){}

//输出css

.test {

  font-size: 18px;

  color: #ffffff;

}

.test ul {

  width: 100px;

  height: 50px;

}

.test ul li,

.study {

  float: left;

  margin-right: 10px;

  width: 50px;

  height: 50px;

}