CSS---常用

flex布局：https://www.runoob.com/bootstrap4/bootstrap4-flex.html

http://www.ruanyifeng.com/blog/2015/07/flex-grammar.html

1.超出div的内容隐藏

overflow:hidden

2.只读

readonly

3.图片设置缩放

只要设置宽度或这长度即可

3.给图片剧中

            <el-col :span="4" style="height: 100px;display: flex;justify-content: center;align-items: center;">  //div需要设置宽度
                <img style="height: 50px;border-radius: 50px;margin: 0 auto" src="@/assets/touxiang.jpg" alt="">
            </el-col>