Nicholai
75168f7678
structure: state/CURRENT.md — 2-4 line session state (rewritten each session) events/ — json event bus (pull-based, optional context) persistent/ — important decisions (one doc per decision) emit — helper script for emitting events
36 lines
1018 B
Markdown
36 lines
1018 B
Markdown
---
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title: Do not wrap a simple expression with a primitive result type in useMemo
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impact: LOW-MEDIUM
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impactDescription: wasted computation on every render
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tags: rerender, useMemo, optimization
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---
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## Do not wrap a simple expression with a primitive result type in useMemo
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When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`.
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Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself.
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**Incorrect:**
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```tsx
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function Header({ user, notifications }: Props) {
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const isLoading = useMemo(() => {
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return user.isLoading || notifications.isLoading
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}, [user.isLoading, notifications.isLoading])
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if (isLoading) return <Skeleton />
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// return some markup
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}
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```
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**Correct:**
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```tsx
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function Header({ user, notifications }: Props) {
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const isLoading = user.isLoading || notifications.isLoading
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if (isLoading) return <Skeleton />
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// return some markup
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}
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```
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