wehub-skill-sync
45 lines
1.1 KiB
Markdown
45 lines
1.1 KiB
Markdown
---
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title: Extract to Memoized Components
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impact: MEDIUM
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impactDescription: 支持提前返回
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tags: rerender, memo, useMemo, optimization
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---
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## 提取为记忆化组件
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将耗时工作提取为记忆化组件，以便在计算前支持提前返回。
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**错误做法（即使在加载时也会计算头像）：**
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```tsx
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function Profile({ user, loading }: Props) {
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const avatar = useMemo(() => {
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const id = computeAvatarId(user)
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return <Avatar id={id} />
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}, [user])
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if (loading) return <Skeleton />
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return <div>{avatar}</div>
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}
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```
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**正确做法（加载时跳过计算）：**
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```tsx
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const UserAvatar = memo(function UserAvatar({ user }: { user: User }) {
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const id = useMemo(() => computeAvatarId(user), [user])
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return <Avatar id={id} />
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})
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function Profile({ user, loading }: Props) {
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if (loading) return <Skeleton />
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return (
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<div>
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<UserAvatar user={user} />
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</div>
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)
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}
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```
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**注意：** 如果你的项目已启用 [React Compiler](https://react.dev/learn/react-compiler)，则无需手动使用 `memo()` 和 `useMemo()` 进行记忆化。编译器会自动优化重渲染。
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