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useMemo

useMemo

Intermediatereact1 min read
use memomemoized valuememo hookderived state
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Definition

A React hook that memoizes an expensive computation so it's not recalculated on every render.

خطاف React يحفظ عملية حسابية مكلفة في الذاكرة المؤقتة حتى لا تُعاد حسابها عند كل تصيير.

Why It Matters

The glossary index on 404Fault is built from 155+ terms with `useMemo` — without it, the index would rebuild on every character typed in the search box, causing lag.

فهرس المصطلحات في 404Fault مبني من 155+ مصطلح بـ`useMemo` — بدونه، سيُعاد بناء الفهرس عند كل حرف مكتوب في خانة البحث، مما يسبب تأخيرًا.

Full Definition

useMemo accepts a function and dependency array. It runs the function on mount and re-runs it only when dependencies change, caching the result between renders. Used for expensive derived values: filtering/sorting large arrays, building search indexes, computing aggregate stats. The glossary page uses `useMemo(() => buildGlossaryIndex(terms), [terms])` to avoid rebuilding the search index on every keystroke.
useMemo يقبل دالة ومصفوفة تبعيات. يُشغّل الدالة عند التثبيت ويُعيد تشغيلها فقط عند تغيير التبعيات، مع تخزين النتيجة بين عمليات التصيير. يُستخدم للقيم المشتقة المكلفة.

Example Usage

“const index = useMemo(() => buildGlossaryIndex(terms), [terms]); const filtered = useMemo(() => searchGlossaryIndex(index, search), [index, search]);”

“const index = useMemo(() => buildGlossaryIndex(terms), [terms]); const filtered = useMemo(() => searchGlossaryIndex(index, search), [index, search]);”

Knowledge Graph

AI Builder Tips

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Avoid these mistakes when using useMemo:

1

Overusing useMemo for cheap computations — the memoization overhead can be larger than the computation itself

2

Incorrect dependencies causing stale cached values

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Help me build a project using useMemo.

Explain:
1. What is useMemo and why it matters
2. The core architecture and required tools
3. Step-by-step implementation plan
4. Common mistakes to avoid: Overusing useMemo for cheap computations — the memoization overhead can be larger than the computation itself, Incorrect dependencies causing stale cached values
5. Best practices and production tips

Official Resources

Official Documentation
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