Core Concepts

Middleware

Intercept and modify requests before they reach your route handlers with an async-first pipeline.

Authentication

Protect routes with auth middleware

Rate Limiting

Built-in rate limiting protection

Logging

Request logging with timing

CORS

Cross-origin configuration

Creating Middleware

Middleware functions receive request, response, and next.

middleware.ts

1import { CanxRequest, CanxResponse, NextFunction } from "canxjs";
2
3const myMiddleware = async (
4  req: CanxRequest, 
5  res: CanxResponse, 
6  next: NextFunction
7) => {
8  console.log("Request started:", req.method, req.path);
9  const result = await next();
10  console.log("Request completed");
11  return result;
12};

Applying Middleware

Apply globally, to specific routes, or route groups.

app.ts

1import { createApp, logger, cors } from "canxjs";
2
3const app = createApp({ port: 3000 });
4
5// Global middleware
6app.use(logger());
7app.use(cors());
8
9// Route-specific middleware
10app.get("/admin", authMiddleware, adminHandler);
11
12// Group middleware
13app.group("/api", (router) => {
14  router.middleware(authMiddleware);
15  router.get("/profile", profileHandler);
16});

Authentication Middleware

auth.ts

1export const authMiddleware = async (req, res, next) => {
2  const token = req.header("authorization")?.replace("Bearer ", "");
3  
4  if (!token) {
5    return res.status(401).json({ error: "Unauthorized" });
6  }
7  
8  try {
9    const user = await verifyToken(token);
10    req.context.set("user", user);
11    return next();
12  } catch (error) {
13    return res.status(401).json({ error: "Invalid token" });
14  }
15};

Built-in Middleware

Middleware	Description
logger()	Logs request details
cors(opts)	CORS configuration
rateLimit(opts)	Rate limit by IP
compress()	Gzip compression

app.ts

1import { createApp, logger, cors, rateLimit, compress } from "canxjs";
2
3const app = createApp({ port: 3000 });
4
5app.use(logger());  // Logs: [2024-01-15] GET /api/users - 12ms
6
7app.use(cors({
8  origin: ["https://example.com"],
9  credentials: true
10}));
11
12app.use(rateLimit({ windowMs: 60000, max: 100 }));
13
14app.use(compress());

Error Handling

errorHandler.ts

1const errorHandler = async (req, res, next) => {
2  try {
3    return await next();
4  } catch (error) {
5    console.error("[Error]", error);
6    return res.status(500).json({ error: "Internal server error" });
7  }
8};
9
10app.use(errorHandler);

Next Steps

Learn about Request and Response objects.