元素上的位置 ::after 箭头

Question

我做了这个，但我无法将箭头定位到元素的左侧：

但我想要这个：

我的css代码：

export const ClosedStyled = styled.ul<DropDown>`
  ${ListItem}:hover & {
    max-width: 400px !important;
    max-height: 400px !important;
  }
  max-height: 0px !important;
  overflow: hidden;
  -webkit-transition: all 0.2s;
  -moz-transition: all 0.2s;
  -ms-transition: all 0.2s;
  -o-transition: all 0.2s;
  transition: all 0.2s;
  list-style-type: none;
  margin: 0;
  padding: 0;
  top: 0;
  left: 100%;
  font-weight: 400;
  position: absolute;
  padding: 0px;
  z-index: 2;
  background: ${shade(0.4, '#3c8dbc')};
  border-top-right-radius: 5px;
  border-bottom-right-radius: 5px;
  :before {
    content: '';
   position: absolute;
   left: 0px;
   top: 0px;
   width: 0;
   height: 0;
   border-left: 20px solid transparent;
   border-right: 20px solid transparent;
   border-top: 20px solid #000;
   clear: both;
`;

我用的是css in JS with emotion JS，但是问题基本上就是CSS 我使用了 ::after 和边框，但我不知道如何像示例照片

那样翻转它

示例：

https://codesandbox.io/s/cranky-hamilton-oy47v?file=/src/styled.js

Answer 1

好的，我可以正常使用了，但是有一些问题：

ClosedStyled，应该 display 属性而不是宽度和高度，一旦用户悬停它应该是 display:block，否则它应该是 display:none.
ClosedStyled溢出是问题的根本原因，只需将其删除即可看到箭头

这是一个codesandbox

或者您可以在此处查看更改后的代码：

import styled from "@emotion/styled/macro";
import { shade } from "polished";
import { css } from "@emotion/core";
// Global Containers
const Container = styled.div`
  height: 100%;
`;

const Main = styled.div`
  display: flex;
  height: calc(100% - 55px);
  position: relative;
  z-index: 0;
`;
// Global Containers
export const Global = {
  Container,
  Main
};
// header Nav
export const NavBar = styled.div`
  height: 55px;
  background: #3c8dbc;
  display: flex;
  box-shadow: 0 2px 2px rgba(0, 0, 0, 0.05), 0 1px 0 rgba(0, 0, 0, 0.05);
  position: relative;
  z-index: 1;
`;

export const LogoSide = styled.div`
  display: flex;
  background: red;
  justify-content: center;
  background: #3c8dbc;
  padding: 10px;
  width: 100%;
  max-width: 250px;
  height: 55px;
  img {
    height: 35px;
    transition: all 0.2s ease;
  }
`;
// header Nav
export const Header = {
  NavBar,
  LogoSide
};
// SideBar
const SideBodyWrap = styled.nav`
  height: 100%;
  max-width: 250px;
  width: 100%;
  color: #009688;
  background: #3c8dbc;
  transition: all 0.2s ease;
  ::-webkit-scrollbar {
    width: 5px;
  }

  ::-webkit-scrollbar-track {
    -webkit-box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.3);
  }

  ::-webkit-scrollbar-thumb {
    background: rgba(255, 0, 0, 0.8);
    -webkit-box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.5);
  }
  ::-webkit-scrollbar-thumb:window-inactive {
    background: rgba(255, 0, 0, 0.4);
  }
`;

const MenuList = styled.ul`
  font-family: "Ubuntu";
  font-size: 14px;
  font-weight: 300;
  text-decoration: none;
  color: #fff;
  padding-top: 10px;
`;

export const ListItem = styled.li`
  display: flex;
  flex-direction: column;
  justify-content: center;
  cursor: pointer;
  position: relative;
`;

export const ListWrap = styled.div`
  padding: 12px 20px 12px 20px;
  display: flex;
  transition: all 0.5s cubic-bezier(0, 1, 0, 1);
  justify-content: center;
  align-items: center;
  a {
    display: flex;
    align-items: center;
    svg {
      margin-right: 15px;
      transition: all 0.5s cubic-bezier(0, 1, 0, 1);
    }
  }
  & .icon-li {
    margin-right: 10px;
  }
  & .down-up_svg,
  .li-name {
    display: none;
  }
`;
export const ClosedStyled = styled.ul`
  ${ListItem}:hover & {
    display: block;
  }
  display: none;
  max-height: 400px !important;
  max-width: 400px !important;
  -webkit-transition: all 0.2s;
  -moz-transition: all 0.2s;
  -ms-transition: all 0.2s;
  -o-transition: all 0.2s;
  transition: all 0.2s;
  list-style-type: none;
  margin: 0;
  padding: 0;
  top: 0;
  left: 100%;
  font-weight: 400;
  position: absolute;
  padding: 0px;
  z-index: 2;
  background: ${shade(0.4, "#3c8dbc")};
  border-top-right-radius: 5px;
  border-bottom-right-radius: 5px;
  :after {
    content: "";
    position: absolute;
    left: -15px;
    top: 8px;
    width: 0;
    overflow: hidden;
    height: 0;
    border-top: 15px solid transparent;
    border-bottom: 15px solid transparent;
    border-right: 15px solid blue;
    clear: both;
    z-index: 11;
  }
  & .li-closed {
    white-space: nowrap;
    padding: 10px 20px;
    :hover > svg {
      color: orange;
    }
    svg {
      margin-right: 10px;
    }
  }
  a {
    font-family: "Ubuntu";
    font-size: 14px;
    font-weight: 300;
    text-decoration: none;
    color: #8aa4af;
  }
`;

const DashMenu = styled.div`
  display: flex;
  flex-direction: column;
`;

export const SideBar = {
  SideBodyWrap,
  DashMenu,
  ClosedStyled,
  ListItem,
  ListWrap,
  MenuList
};
// SideBar

export const Content = styled.div`
  height: 100%;
  width: 100%;
  background: #eee;
`;

元素上的位置 ::after 箭头

Position ::after arrow on element

html

javascript

css

emotion