Hari 23: TypeScript di Node.js & Express

55 min Last updated 09 Apr 2026

Type-safe Express Routes (Simulasi)

// Type untuk request/response Express
interface Request {
    params: P;
    query: Q;
    body: B;
}

interface Response {
    json: (data: unknown) => void;
    status: (code: number) => Response;
    send: (data: string) => void;
}

// Route handler type
type Handler =
    (req: Request, res: Response) => void | Promise;

// Type-safe route definitions
type UserParams = { id: string };
type UserQuery  = { include?: "posts" | "profile" };
type CreateUserBody = { nama: string; email: string; password: string };

const getUser: Handler = (req, res) => {
    const { id } = req.params;           // string
    const include = req.query.include;   // "posts" | "profile" | undefined
    res.json({ id, include });
};

💡 Notice: Map<string, Handler> sebagai router sangat efisien (O(1) lookup). Pattern ini mirip dengan implementasi internal Express.js.

Assignment

Buat type-safe router sederhana. Router menyimpan handlers per method+path, dan bisa dipanggil untuk simulate request.

Expected output:

GET /users: [{"id":1,"nama":"Budi"}]

POST /users: {"id":2,"nama":"Sari","email":"s@s.com"}

GET /users/:id: {"id":"1","nama":"Budi"}

TS index.ts

type Method = "GET" | "POST" | "PUT" | "DELETE";
type Handler = (req: { params: Record<string, string>; body?: any }) => any;

class Router {
    private routes: Map<string, Handler> = new Map();

private add(method: Method, path: string, handler: Handler): this {
        this.routes.set(`${method}:${path}`, handler);
        return this;
    }

get  = (path: string, h: Handler) => this.add("GET",    path, h);
    post = (path: string, h: Handler) => this.add("POST",   path, h);
    put  = (path: string, h: Handler) => this.add("PUT",    path, h);
    del  = (path: string, h: Handler) => this.add("DELETE", path, h);

handle(method: Method, path: string, req: any = {}): void {
        const handler = this.routes.get(`${method}:${path}`);
        if (!handler) { console.log(`404: ${method} ${path}`); return; }
        const result = handler(req);
        console.log(`${method} ${path}: ${JSON.stringify(result)}`);
    }
}

router.handle("GET",  "/users");
router.handle("POST", "/users", { body: { nama: "Sari", email: "s@s.com" } });
router.handle("GET",  "/users/:id", { params: { id: "1" } });

Solution

type Method = "GET" | "POST" | "PUT" | "DELETE";
type Handler = (req: { params: Record<string, string>; body?: any }) => any;

class Router {
    private routes: Map<string, Handler> = new Map();

private add(method: Method, path: string, handler: Handler): this {
        this.routes.set(`${method}:${path}`, handler);
        return this;
    }

router.handle("GET",  "/users");
router.handle("POST", "/users", { body: { nama: "Sari", email: "s@s.com" } });
router.handle("GET",  "/users/:id", { params: { id: "1" } });

Output