typescript / intermediate
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
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function fetchData() {return { id: 1, name: "Alice", active: true };}type UserProfile = ReturnType<typeof fetchData>;const user: UserProfile = {id: 2,name: "Bob",active: false};
Breakdown
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type UserProfile = ReturnType<typeof fetchData>;
Uses 'typeof' to get the function signature and 'ReturnType' to isolate what it returns.