原文链接：https://emotion.sh/docs/styled

styled是一种创建带有样式的React组件的方法

1.写一个带样式的组件

语法：styled.元素名`样式`

import styled from '@emotion/styled'
const Button = styled.button`
  color: turquoise;
`
render(<Button>This my button component.</Button>)

2.通过参数控制样式

import styled from '@emotion/styled'
import {Fragment} from 'react';
const Button = styled.button`
  color: ${props =>
    props.primary ? 'hotpink' : 'turquoise'};
`
<Fragment>
  <Button primary>This is a primary button.</Button>
  <Button>This is a primary button.</Button>
</Fragment>

3.通过传className创建组件

语法：styled( ({className}) => (<p className={className}>text</
p>) )`样式`
分析：相当于把样式通过className传递给了元素

import styled from '@emotion/styled'
const Basic = ({ className }) => (
  <div className={className}>Some text</div>
)
const Fancy = styled(Basic)`
  color: hotpink;
`
render(<Fancy />)

4.创建与某个组件相同的样式

语法：样式组件.withComponent('元素')

import styled from '@emotion/styled'
const Section = styled.section`
  background: #333;
  color: #fff;
`
// Aside样式跟Section样式相同
const Aside = Section.withComponent('aside')
render(
  <div>
    <Section>This is a section</Section>
    <Aside>This is an aside</Aside>
  </div>
)

5.嵌套写法 - ${子组件}

语法：父组件 = styled.元素`${子组件} {样式}`

import styled from '@emotion/styled'
const Child = styled.div`
  color: red;
`
const Parent = styled.div`
  ${Child} {
    color: green;
  }
`
render(
  <div>
    <Parent>
      <Child>Green because I am inside a Parent</Child>
    </Parent>
    <Child>Red because I am not inside a Parent</Child>
  </div>
)

6.嵌套写法 - 对象(键值对)

语法：父组件 = styled.元素(
{
[子组件]: {样式}}
)

import styled from '@emotion/styled'
const Child = styled.div({
  color: 'red'
})
const Parent = styled.div({
  [Child]: {
    color: 'green'
  }
})
render(
  <div>
    <Parent>
      <Child>green</Child>
    </Parent>
    <Child>red</Child>
  </div>
)

7.对象样式

import styled from '@emotion/styled'
const H1 = styled.h1(
  {
    fontSize: 20
  },
  props => ({ color: props.color,  width:props.width })
)
render(<H1 color="lightgreen" width="200px">This is lightgreen.</H1>)

8.

import isPropValid from '@emotion/is-prop-valid'
import styled from '@emotion/styled'

const H1 = styled('h1', {
  shouldForwardProp: prop =>
    isPropValid(prop) && prop !== 'color'
})(props => ({
  color: 'hotpink'
}))

render(<H1 color="lightgreen">This is lightgreen.</H1>)

9.动态样式

import styled from '@emotion/styled'
import { css } from '@emotion/core'
const dynamicStyle = props =>
  css`
    color: ${props.color};
  `
const Container = styled.div`
  ${dynamicStyle};
`
render(
  <Container color="lightgreen">
    This is lightgreen.
  </Container>
)

10.as prop

要使用样式化组件中的样式但要更改呈现的元素，可以使用as prop。

import styled from '@emotion/styled'

const Button = styled.button`
  color: hotpink;
`
render(
  <Button
    as="a"
    href="https://github.com/emotion-js/emotion"
  >
    Emotion on GitHub
  </Button>
)

11.嵌套元素样式写法

import styled from '@emotion/styled'
const Example = styled('span')`
  color: lightgreen;
  & > a {
    color: hotpink;
  }
`
render(
  <Example>
    This is <a>nested</a>.
  </Example>
)