TypeScript Generics: A Practical Guide for Backend Developers

TypeScript Generics: A Practical Guide for Backend Developers Generics let you write reusable, type-safe code without duplicating functions or using any. The Basics function getFirst < T > ( items : T []): T | undefined { return items [ 0 ]; } const num = getFirst ([ 1 , 2 , 3 ]); // type: number Generic API Response interface ApiResponse < T > { data : T ; meta : { page : number ; total : number }; } async function fetchPaginated < T > ( url : string ): Promise < ApiResponse < T >> { return ( await fetch ( url )). json (); } Generic Repository class Repository < T extends HasId > { constructor ( private collection : string ) {} async findById ( id : string ): Promise < T | null > { return db . collection ( this . collection ). findOne ({ id }); } async create ( data : Omit < T , " id " > ): Promise < T > { const doc = { ... data , id : randomUUID () } as T ; await db . collection ( this . collection ). insertOne ( doc ); return doc ; } } Utility Types Partial, Pick, Omit, Record Part