TypeScript ships a library of utility types that transform an existing type into a new one without repeating field definitions.
ts
interface Token { symbol: string; decimals: number; totalSupply: number; }
type TokenPatch = Partial<Token>; // all fields optional
type TokenSummary = Pick<Token, "symbol" | "decimals">; // only these fields
type TokenWithoutSupply = Omit<Token, "totalSupply">; // all except this one
function updateToken(id: string, patch: Partial<Token>) { /* ... */ }
updateToken("1", { decimals: 6 }); // OK: other fields optional`Required<T>` is the opposite of `Partial` (forces all fields to be required), and `Readonly<T>` makes every field `readonly`. Composing these keeps a single source of truth (`Token`) instead of hand-maintaining several near-duplicate interfaces.