谁能告诉我为什么在不处理样式组件之前？

Question

I'm try to use before on style components on React but it's not working. Without before background image shown but after adding this before background image not showing;

import styled from  'styled-components'
export const Container=styled.div `
&:before {
content:'';
top:0px;
left:0px;
right:0px;
position:absolute;
background-image:url(${({bg})=>bg});
background-size:cover;
}
`;

Answer 1

try::before with double ":" Also give some height/width