40 lines
983 B
Markdown
40 lines
983 B
Markdown
---
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title: Defer State Reads to Usage Point
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impact: MEDIUM
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impactDescription: avoids unnecessary subscriptions
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tags: rerender, searchParams, localStorage, optimization
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---
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## Defer State Reads to Usage Point
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Don't subscribe to dynamic state (searchParams, localStorage) if you only read it inside callbacks.
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**Incorrect (subscribes to all searchParams changes):**
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```tsx
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function ShareButton({ chatId }: { chatId: string }) {
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const searchParams = useSearchParams();
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const handleShare = () => {
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const ref = searchParams.get("ref");
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shareChat(chatId, { ref });
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};
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return <button onClick={handleShare}>Share</button>;
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}
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```
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**Correct (reads on demand, no subscription):**
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```tsx
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function ShareButton({ chatId }: { chatId: string }) {
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const handleShare = () => {
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const params = new URLSearchParams(window.location.search);
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const ref = params.get("ref");
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shareChat(chatId, { ref });
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};
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return <button onClick={handleShare}>Share</button>;
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}
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```
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