Typing Express Routes - Quick Guide

1Request<Params, ResBody, ReqBody, ReqQuery, Locals>;

1// POST /tournaments
2export type CreateTournamentRequest = Request<null, CreateTournamentInput>;
3
4// Usage in handler
5static async createTournament(req: CreateTournamentRequest, res: Response) {
6  const { label, mode } = req.body; // Typed as CreateTournamentInput
7}

1// GET /tournaments/:tournamentId
2export type GetTournamentRequest = Request<{ tournamentId: string }>;
3
4// Usage in handler
5static async getTournament(req: GetTournamentRequest, res: Response) {
6  const { tournamentId } = req.params; // Typed as string
7}

1// Handles both POST /tournaments and GET /tournaments/:tournamentId
2export type TournamentRequest = Request<{ tournamentId?: string }, CreateTournamentInput>;
3
4// Usage
5static async handleTournament(req: TournamentRequest, res: Response) {
6  const tournamentId = req.params.tournamentId; // string | undefined
7  const body = req.body; // CreateTournamentInput
8}

1// GET /tournaments/:tournamentId/rounds/:roundId
2export type TournamentRoundRequest = Request<{
3  tournamentId: string;
4  roundId: string;
5}>;

1// GET /tournaments?page=1&limit=10
2export type TournamentListRequest = Request<
3  null, // No route params
4  unknown, // Response body (handled separately)
5  unknown, // Request body
6  { page?: string; limit?: string } // Query params
7>;

1// Good: Specific types
2export type CreateTournamentRequest = Request<null, CreateTournamentInput>;
3export type UpdateTournamentRequest = Request<{ tournamentId: string }, UpdateTournamentInput>;
4
5// Avoid: Generic any types
6export type GenericRequest = Request<any, any>;

1// Handles multiple route patterns
2export type TournamentRequest = Request<
3  {
4    tournamentId?: string;
5    roundId?: string;
6  },
7  TournamentInput
8>;

1// Tournament-related types
2export namespace TournamentTypes {
3  export type CreateRequest = Request<null, CreateTournamentInput>;
4  export type GetRequest = Request<{ tournamentId: string }>;
5  export type UpdateRequest = Request<{ tournamentId: string }, UpdateTournamentInput>;
6}

1// Base authenticated request
2interface AuthenticatedRequest<P = null, B = unknown> extends Request<P, unknown, B> {
3  authenticatedUser?: User;
4}
5
6// Specific tournament request with auth
7export type AuthenticatedTournamentRequest = AuthenticatedRequest<{ tournamentId: string }, CreateTournamentInput>;

1// Bad
2export type BadRequest = Request<any, any>;

1// Bad: Will break on routes without tournamentId
2export type BadTournamentRequest = Request<{ tournamentId: string }>;
3
4// Good: Works for both parameterized and non-parameterized routes
5export type GoodTournamentRequest = Request<{ tournamentId?: string }>;

1// Bad: tournamentId required but used on routes without it
2router.post('/tournaments', handler); // No tournamentId in route
3// Type expects tournamentId but route doesn't provide it

1// types.ts
2export interface CreateTournamentInput {
3  label: string;
4  mode: string;
5}
6
7export type TournamentRequest = Request<{ tournamentId?: string }, CreateTournamentInput>;
8
9// routes.ts
10import { TournamentRequest } from './types';
11
12router.post('/tournaments', (req: TournamentRequest, res: Response) => {
13  // req.body is typed as CreateTournamentInput
14  // req.params.tournamentId is undefined
15});
16
17router.get('/tournaments/:tournamentId', (req: TournamentRequest, res: Response) => {
18  // req.params.tournamentId is string
19  // req.body is CreateTournamentInput (though not used in GET)
20});