Extracting Types with ReturnType

Snippet

Extracting Types with ReturnType

The ReturnType utility type extracts the return type of a function. This ensures that if the function's implementation changes, the dependent types update automatically, maintaining a single source of truth.

snippet.ts
typescript
function fetchData() {
  return { id: 1, name: "Alice", active: true };
}
 
type UserProfile = ReturnType<typeof fetchData>;
 
const user: UserProfile = {
  id: 2,
  name: "Bob",
  active: false
};

Breakdown

type UserProfile = ReturnType<typeof fetchData>;

Uses 'typeof' to get the function signature and 'ReturnType' to isolate what it returns.

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Extracting Types with ReturnType

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