第七周

date

May 24, 2022

slug

week-7

styled-components 记录

最近看 CSS for JS 课程，看到作者分享使用 styled-components 的一些技巧，感觉很有用，所以记录总结一下。

Demystifying styled-components The styled-components Happy Path

基础的处理逻辑

当我们使用 styled-components 生成一个组件的时候会发生下面代码这几件事：

const styled = (Tag) => (styles) => {
  return function NewComponent(props) {
		// 生成唯一 class 名
    const uniqueClassName = comeUpWithUniqueName(styles);
    // 加工 style 字符串
		const processedStyles = runStylesThroughStylis(styles);
    // style 字符注入 css 文件
    createAndInjectCSSClass(uniqueClassName, styles);
		// 新的 className 和组件本身的 className 组合
		const combinedClasses =
      [uniqueClassName, props.className].join(' ');

		// 绑定 className
    return <Tag className={combinedClasses} {...props} />
  }
}

模板字符使用 props 后会生成两个份不一样的 className 和 CSS

因为 props 对象里的值是暂时无法确定的，必须等到运行后才能确定

/* before */
const ContentImage = styled.img`
  display: block;
  margin-bottom: 8px;
  width: 100%;
  max-width: ${p => p.maxWidth};
`;

render(
  <>
    <ContentImage
      alt="A running shoe with pink laces and a rainbow decal"
      src="/images/shoe.png"
      maxWidth="200px"
    />
    <ContentImage
      alt="A close-up shot of the same running shoe"
      src="/images/shoe-closeup.png"
    />
  </>
)

/* after */
<style>
  .JDSLg {
    display: block;
    margin-bottom: 8px;
    width: 100%;
    max-width: 200px;
  }
  .eXyedY {
    display: block;
    margin-bottom: 8px;
    width: 100%;
  }
</style>
<img
  alt="A running shoe with pink laces and a rainbow decal"
  src="/images/shoe.png"
  class="sc-bdnxRM JDSLg"
/>
<img
  alt="A close-up shot of the same running shoe"
  src="/images/shoe-closeup.png"
  class="sc-bdnxRM eXyedY"
/>

使用 CSS 变量会生成更少的代码，减少摩擦

例如下面的 var(—max-width)，配合 style 对象参数，它们会共享一个 className 和 CSS 代码。

/* before */
const ContentImage = styled.img`
  display: block;
  margin-bottom: 8px;
  width: 100%;
  max-width: var(--max-width);
`;

render(
  <>
    <ContentImage
      alt="A running shoe with pink laces and a rainbow decal"
      src="/images/shoe.png"
      style={{
        '--max-width': '200px',
      }}
    />
    <ContentImage
      alt="A close-up shot of the same running shoe"
      src="/images/shoe-closeup.png"
    />
  </>
)

/* after */
<style>
  .JDSLg {
    display: block;
    margin-bottom: 8px;
    width: 100%;
    max-width: var(--max-width);
  }
</style>
<img
  alt="A running shoe with pink laces and a rainbow decal"
  src="/images/shoe.png"
  class="sc-bdnxRM JDSLg"
  style="--max-width: 200px"
/>
<img
  alt="A close-up shot of the same running shoe"
  src="/images/shoe-closeup.png"
  class="sc-bdnxRM JDSLg"
/>

组件单一样式控制

有两种适用的场景，一个场景是两个组件都是通用组件，会频繁适用，与业务逻辑不强关联

// Aside.js
const Aside = ({ children }) => { /* Omitted for brevity */ }
// Export this wrapper
export const Wrapper = styled.aside`
  /* styles */
`;
export default Aside;

// TextLink.js
import { Wrapper as AsideWrapper } from '../Aside'

const TextLink = styled.a`
  color: var(--color-primary);
  font-weight: var(--font-weight-medium);
  ${AsideWrapper} & {
    color: var(--color-text);
    font-weight: var(--font-weight-bold);
  }
`;

// render after
.TextLink-abc123 {
  color: var(--color-primary);
  font-weight: var(--font-weight-medium);
}
.Aside-Wrapper-def789 .TextLink-abc123 {
  color: var(--color-text);
  font-weight: var(--font-weight-bold);
}

还有一种是在某种业务情况下使用，与当前的业务有较强的关联

import TextLink from '../TextLink';
import { Wrapper as AsideWrapper } from '../Aside'

const HalloweenTextLink = styled(TextLink)`
	--color-primary: orange;
  font-family: 'Spooky Font', cursive;
`;

// render css
.TextLink-abc123 {
  color: var(--color-primary);
  font-weight: var(--font-weight-medium);
}

.HalloweenTextLink-edf321 {
	--color-primary: orange;
}

<div
	class="TextLink-abc123 HalloweenTextLink-edf321"
>
	hello!
</div>

as 语义化

Extending Styles

不要让包裹的标签全是 div，可以根据语义使用 as 指定包裹的标签

// `level` is a number from 1 to 6, mapping to h1-h6
function Heading({ level, children }) {
  const tag = `h${level}`;
  return (
    <Wrapper as={tag}>
      {children}
    </Wrapper>
  );
}
// The `h2` down here doesn't really matter,
// since it'll always get overwritten!
const Wrapper = styled.h2`
  /* Stuff */
`;

function LinkButton({ href, children, ...delegated }) {
  const tag = typeof href === 'string'
    ? 'a'
    : 'button';
  return (
    <Wrapper as={tag} href={href} {...delegated}>
      {children}
    </Wrapper>
  );
}