Unawezaje kuzuia usasishaji wa state usisababishe re-renders nyingi kupita kiasi?

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Mabadiliko ya state huchochea re-renders, na state iliyoundwa vibaya inaweza kusababisha **re-rendering nyingi zaidi kuliko inavyohitajika** — ikifanya app kuwa polepole. Mikakati muhimu: jisajili kwa ufinyu, gawanya state, memoize, na weka state ya ndani (local). ## 1. Jisajili kwa kipande kidogo zaidi unachohitaji ```jsx // ❌ subscribing to the whole store → re-renders on ANY change const store = useStore(); const count = store.count; // ✅ select only what you use → re-renders only when `count` changes const count = useStore((s) => s.count); ``` Usajili wa kuchagua (selective subscriptions) (Zustand/Redux selectors, Jotai atoms) ndio nyenzo kubwa zaidi — vipengele hu-re-render tu wakati kipande chao mahususi kinabadilika, si kwa kila usasishaji wa store. ## 2. Gawanya state / context ili kupunguza eneo la athari ```jsx // ❌ one big context → every consumer re-renders when anything changes // ✅ separate contexts so unrelated updates don't cross-trigger ... ``` ## 3. Memoize vipengele na thamani ```jsx const Item = React.memo(ItemComponent); // skip re-render if props are unchanged const expensiveValue = useMemo(() => compute(data), [data]); const handleClick = useCallback(() => doX(id), [id]); // stable function reference ``` Memoization huzuia vipengele watoto kufanya re-render wakati props zao (kwa reference) hazijabadilika — lakini inafanya kazi tu ikiwa pia unaweka props/callbacks zikiwa thabiti kireferensi (hivyo `useCallback`/`useMemo`) na kusasisha state **kwa njia ya immutable**. ## 4. Weka state ya ndani kadiri iwezekanavyo ```text State high in the tree re-renders everything below it. Move state DOWN to the smallest component that needs it → smaller re-render scope. ``` ## 5. Usihifadhi thamani zilizotokana (derived); epuka references mpya kila render ```jsx // ❌ a new object/array each render breaks memoization downstream // new {} every render // ✅ stable reference const config = useMemo(() => ({ a: 1 }), []); ``` ## 6. Tumia memoized selectors kwa data iliyotokana ```js const selectActive = createSelector([s => s.items], items => items.filter(i => i.active)); // returns the SAME reference when items didn't change → no needless re-render ``` ## Pima kwanza ```text React DevTools Profiler / "why did you render" → find what actually re-renders before optimizing. Premature memoization adds complexity for no gain. ``` ## Kwa nini ni muhimu Re-renders za kupita kiasi ni mojawapo ya sababu kuu za apps za React/zinazoendeshwa na state kuwa nzito, nazo zinatokana na jinsi state ilivyoundwa na kusajiliwa. Vifaa — usajili finyu wa kuchagua, kugawanya contexts, memoization yenye references thabiti, usasishaji wa immutable, na kuweka state ya ndani — vinadhibiti moja kwa moja eneo la re-render. Muhimu zaidi, unapaswa **kupima** (Profiler) ili kupata kizuizi halisi kabla ya kuboresha, kwa kuwa memoization isiyokuwa makini huongeza utata bila manufaa. Kuelewa nini huchochea re-renders na jinsi ya kuzidhibiti ni muhimu kwa apps zenye utendaji wa kiwango kikubwa.