Setup

Buat & Jalankan Server

const express = require("express");
const app = express();
app.listen(3000, () => console.log("Running on :3000"));

Middleware Bawaan

app.use(express.json());          // parse JSON bodies
app.use(express.urlencoded({ extended: true })); // form data
app.use(express.static("public")); // serve static files

Routing

HTTP Method

app.get("/users", (req, res) => res.json(users));
app.post("/users", (req, res) => res.status(201).json(req.body));
app.put("/users/:id", (req, res) => res.json(updated));
app.delete("/users/:id", (req, res) => res.sendStatus(204));

Parameter Route

app.get("/users/:id", (req, res) => {
  const { id } = req.params;
  res.json({ id });
});

Query String

// GET /search?q=express&page=2
app.get("/search", (req, res) => {
  const { q, page } = req.query;
  res.json({ q, page });
});

Middleware

Level Aplikasi

app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  next();
});

Level Route

const auth = (req, res, next) => {
  if (!req.headers.authorization) return res.sendStatus(401);
  next();
};
app.get("/secret", auth, (req, res) => res.json({ ok: true }));

Urutan Eksekusi

app.use(fn)	Berjalan pada setiap request (berurutan)
app.use(path, fn)	Berjalan hanya pada prefix path yang cocok
next()	Teruskan kontrol ke middleware berikutnya
next(err)	Langsung ke error handler

Request & Response

Objek Request

req.params	Parameter route (`/users/:id`)
req.query	Query string (`?key=val`)
req.body	Body request yang diparsing (butuh parser)
req.headers	Objek header request
req.method	HTTP method (GET, POST, ...)
req.path	Pathname URL
req.cookies	Cookie (butuh cookie-parser)

Objek Response

res.json(obj)	Kirim response JSON
res.send(body)	Kirim string/Buffer/objek
res.status(code)	Set HTTP status (bisa di-chain)
res.redirect(url)	Redirect 302 (atau sertakan status)
res.sendFile(path)	Kirim file sebagai response
res.sendStatus(code)	Kirim status dengan teks default
res.set(header, val)	Set header response

Penanganan Error

Middleware Error

// Must have 4 parameters — Express recognizes it as error handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(err.status || 500).json({ error: err.message });
});

Definisikan error handler setelah semua app.use() dan route lainnya

Error Async

// Wrap async route handlers to catch rejections
const wrap = (fn) => (req, res, next) =>
  Promise.resolve(fn(req, res, next)).catch(next);

app.get("/data", wrap(async (req, res) => {
  const data = await fetchData();
  res.json(data);
}));

File Statis

Sajikan Direktori Statis

app.use(express.static("public"));
// serves public/style.css at /style.css

// With virtual path prefix
app.use("/assets", express.static("public"));
// serves public/style.css at /assets/style.css

Opsi

dotfiles	`'ignore'` \| `'allow'` \| `'deny'`
maxAge	Cache-Control max-age dalam ms
index	Nama file index (default: `index.html`)
fallthrough	Teruskan ke middleware berikutnya saat 404

Template

Setup View Engine

app.set("view engine", "ejs");
app.set("views", "./views");

app.get("/", (req, res) => {
  res.render("index", { title: "Home", items: [1, 2, 3] });
});

Engine Umum

ejs	Template JS embedded (`<%= val %>`)
pug	Berbasis indentasi (dulunya Jade)
handlebars	Gaya Mustache (`{{val}}`)

Router

Route Modular

// routes/users.js
const router = require("express").Router();
router.get("/", (req, res) => res.json(users));
router.get("/:id", (req, res) => res.json(user));
module.exports = router;

Mount Router

const usersRouter = require("./routes/users");
app.use("/api/users", usersRouter);
// GET /api/users -> router's "/"
// GET /api/users/5 -> router's "/:id"

Method Router

router.get/post/put/delete	Handler HTTP method
router.use(fn)	Middleware level router
router.param(name, fn)	Pre-proses parameter route
router.route(path)	Chain method pada satu path

Pola Autentikasi

Middleware JWT

const jwt = require("jsonwebtoken");
const auth = (req, res, next) => {
  const token = req.headers.authorization?.split(" ")[1];
  if (!token) return res.sendStatus(401);
  req.user = jwt.verify(token, process.env.SECRET);
  next();
};

Route Terproteksi

app.get("/profile", auth, (req, res) => {
  res.json({ user: req.user });
});
app.use("/api/admin", auth, adminRouter);

Pola Umum

CORS

const cors = require("cors");
app.use(cors());                         // allow all origins
app.use(cors({ origin: "https://example.com" })); // restrict

Environment & Konfigurasi

const port = process.env.PORT || 3000;
app.listen(port);

// Access env in routes
if (app.get("env") === "production") {
  app.use(helmet());
}

Paket npm Berguna

cors	Cross-origin resource sharing
helmet	Header keamanan
morgan	Logger HTTP request
cookie-parser	Parse header Cookie
dotenv	Muat `.env` ke `process.env`
multer	Data form multipart (upload file)

REFERENSI CEPAT EXPRESS.JS