Indexsignatuli ni nini?

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**Indexsignatura** inaeleza aina ya sifa wakati haujui majina yao mapema — kuiga dictionaries/maps ambapo funguo ni dynamike. ```ts interface StringMap { [key: string]: number; // any string key maps to a number } const scores: StringMap = { math: 90, science: 85 }; scores.history = 70; // ✅ any string key allowed scores.math; // number scores.unknownKey; // number (TS assumes it exists!) — a caveat ``` ## Onyo la usalama Kwa indexsignatura ya kawaida, mkutani unachukua **kila** funguo kuwa nayo, kwa hiyo `scores.typo` ni aina ya `number` hata kama ni kweli `undefined` wakati wa utekelezaji. Kuwezesha `noUncheckedIndexedAccess` kunakamatisha hili: ```ts // with noUncheckedIndexedAccess: true scores.math; // number | undefined → forces you to handle the missing case ``` ## Kuchanganya funguo zilizosainiwa na dynamike ```ts interface Config { name: string; // known property [key: string]: string | number; // plus arbitrary extra keys } ``` Sifa zote zilizosainiwa lazima ziwe zinaweza kukalipwa kwa aina ya thamani ya indexsignatura. ## Record mara nyingi ni safi zaidi ```ts type Scores = Record; // same as the index signature type Roles = Record<"admin" | "user", boolean>; // constrained keys ``` `Record` ni kifupi cha idiomatiki na kina msaada wa nchi maalum ya nchi, ambayo `[key: string]` jumla haiwezi. ## Kwa nini kinachohitajika Indexsignatuli kuiga vitu vya funguo-dynamike kweli (meza ya utaftaji, akaches, ramani za JSON zilizochambuliwa). Jua onyo la usalama (`noUncheckedIndexedAccess`) na pendelea `Record` kwa ufahamu — na pendelea `Map` wakati funguo ni kweli wazi na unataka semantiki ya iteration/ukubwa halisi.