Enums ni nini na kwa nini inapaswa kuzitumia?

Question

Accepted Answer

**enum** inafafanua seti ya constants zilizo na jina. TypeScript ina numeric enums na string enums.

```ts
enum Direction { Up, Down, Left, Right } // numeric: Up=0, Down=1, ...
Direction.Up;        // 0
Direction[0];        // "Up" — numeric enums have a reverse mapping

enum Status {        // string enum — more readable values
  Active = "ACTIVE",
  Inactive = "INACTIVE",
}
Status.Active;       // "ACTIVE"
```

## Onyo: enums hutoa runtime code

Takilafu na TypeScript types nyingi (ambazo hupotea wakati wa compilation), `enum` ya kawaida inatoa JavaScript object kwenye bundle yako. Ndiyo sababu timu nyingi zinapendelea **union ya string literals** pamoja na `as const`, ambayo ni aina tu:

```ts
// often preferred — zero runtime cost, easy to read in logs
const Status = { Active: "ACTIVE", Inactive: "INACTIVE" } as const;
type Status = typeof Status[keyof typeof Status]; // "ACTIVE" | "INACTIVE"

// or simply:
type Direction = "up" | "down" | "left" | "right";
```

## const enum

```ts
const enum E { A, B } // inlined at compile time — no runtime object, but has tooling caveats
```

## Kwa nini inapala juhudi

Enums hutoa majina ya maana kwa seti za kudumu (states, roles, directions) na kuzigroupisha chini ya namespace moja.

Lakini kwa sababu yeye hutoa runtime code na ina tabia zisizotaka (numeric enums zimekaguliwa vibaya), TypeScript ya sasa mara nyingi inapendelea **string-literal unions** kwa kesi rahisi — ni nyepesi na kurekebisha data bila matatizo.

Tumia enums wakati unataka namespacing au reverse mapping.