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Update best-practices.mdx #3180

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May 2, 2024
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16 changes: 8 additions & 8 deletions docs/best-practices.mdx
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Expand Up @@ -93,29 +93,29 @@ Advantages of sharing styles via component reuse include:

The css prop or `styled` should be used for static styles, while the `style` prop (inline styles) should be used for truly dynamic styles. By dynamic styles, we mean styles that change frequently or are unique to a single element.

Imagine you are displaying a list of user avatars in a forum application. Every avatar shares certain static CSS, like `width: 40px` and `border-radius: 50%`, but the avatar image is set via a `background-style` rule whose value is different for each avatar. If you pass all of this CSS through the CSS prop, you'll end up with a lot of nearly-duplicate CSS in the document. With 3 avatars, Emotion will create something like:
Imagine you are displaying a list of user avatars in a forum application. Every avatar shares certain static CSS, like `width: 40px` and `border-radius: 50%`, but the avatar image is set via a `background-image` rule whose value is different for each avatar. If you pass all of this CSS through the CSS prop, you'll end up with a lot of nearly-duplicate CSS in the document. With 3 avatars, Emotion will create something like:

```html
<style>
.css-1udhswa {
border-radius: 50%;
width: 40px;
height: 40px;
background-style: url(https://i.pravatar.cc/150?u=0);
background-image: url(https://i.pravatar.cc/150?u=0);
}

.css-1cpwmbr {
border-radius: 50%;
width: 40px;
height: 40px;
background-style: url(https://i.pravatar.cc/150?u=1);
background-image: url(https://i.pravatar.cc/150?u=1);
}

.css-am987o {
border-radius: 50%;
width: 40px;
height: 40px;
background-style: url(https://i.pravatar.cc/150?u=2);
background-image: url(https://i.pravatar.cc/150?u=2);
}
</style>
```
Expand All @@ -141,19 +141,19 @@ CSS variables can be used with the `style` prop to keep the CSS in a single plac
border-radius: 50%;
width: 40px;
height: 40px;
background-style: var(--background-style);
background-image: var(--background-image);
}
```

Then, for each avatar, you render an element which sets the value of the `--background-style` CSS variable:
Then, for each avatar, you render an element which sets the value of the `--background-image` CSS variable:

```tsx
function Avatar({ imageUrl }) {
return <div className="avatar" style={{ '--background-style': imageUrl }} />
return <div className="avatar" style={{ '--background-image': imageUrl }} />
}
```

If you're using TypeScript, you'll have to use a type assertion like `style={{ ['--background-style' as any]: imageUrl }}` as explained [here](https://stackoverflow.com/a/52013197/752601).
If you're using TypeScript, you'll have to use a type assertion like `style={{ ['--background-image' as any]: imageUrl }}` as explained [here](https://stackoverflow.com/a/52013197/752601).

### If using React, prefer `@emotion/react` or `@emotion/styled` over `@emotion/css`

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