TypeScript Tips yang Sering Saya Pakai

type Color = "red" | "green" | "blue";
type Palette = Record<Color, string>;
 
// Tanpa satisfies — tipe hilang
const colors: Palette = {
  red: "#ef4444",
  green: "#22c55e",
  blue: "#3b82f6",
};
// colors.red → string (tidak spesifik)
 
// Dengan satisfies — tipe tetap terjaga
const colors2 = {
  red: "#ef4444",
  green: "#22c55e",
  blue: "#3b82f6",
} satisfies Palette;
// colors2.red → "#ef4444" (string literal)

interface User {
  id: number;
  name: string;
  email: string;
}
 
// Semua field opsional
type PatchUser = Partial<User>;
 
// Semua field wajib
type CompleteUser = Required<Partial<User>>;

// Ambil field tertentu
type UserPreview = Pick<User, "id" | "name">;
 
// Buang field tertentu
type UserWithoutId = Omit<User, "id">;

type Direction = "top" | "bottom" | "left" | "right";
type Padding = `p-${Direction}`;
// "p-top" | "p-bottom" | "p-left" | "p-right"

function isError(value: unknown): value is Error {
  return value instanceof Error;
}
 
try {
  // ...
} catch (e) {
  if (isError(e)) {
    console.log(e.message); // TypeScript tahu ini Error
  }
}