unknown vs any: Pilihan yang Lebih Aman

Selamat Datang

Masalah dengan any

let val: any = getData();
val.someMethod(); // TypeScript: OK. Runtime: possible crash

Memperkenalkan unknown

let val: unknown = getData();
// val.someMethod(); // Error: Object is of type 'unknown'

Mempersempit unknown Sebelum Digunakan

let input: unknown = getInput();
if (typeof input === 'string') {
  console.log(input.toUpperCase()); // OK — narrowed to string
}

unknown Tidak Dapat Ditetapkan ke Tipe Tertentu

let x: unknown = 'hello';
// let s: string = x; // Error
let s: string = x as string; // OK with assertion

Menggunakan unknown dalam Blok Penangkapan Kesalahan

try {
  doSomething();
} catch (err: unknown) {
  if (err instanceof Error) {
    console.log(err.message); // safe
  }
}

unknown untuk Data Eksternal

const raw: unknown = JSON.parse(text);
if (
  typeof raw === 'object' &&
  raw !== null &&
  'name' in raw
) {
  console.log((raw as any).name);
}

Penjaga Tipe dengan unknown

function isUser(val: unknown): val is { name: string } {
  return typeof val === 'object' && val !== null && 'name' in val;
}

unknown vs never

// unknown: anything can be assigned to it
let a: unknown = 42; // OK

// never: nothing can be assigned to it
function fail(): never { throw new Error(); }

Memilih antara any dan unknown

Pustaka Validasi saat Program Berjalan

import { z } from 'zod';
const UserSchema = z.object({ name: z.string(), age: z.number() });
const user = UserSchema.parse(unknownData); // throws if invalid

Pemeriksaan Singkat

Rangkuman