Skip to main content

Express

Setup​

1. Install Express​

npm i express
Auto reload server
npm i -D nodemon
"start": "node src/index.js",
"watch": "nodemon src/index.js --experimental-modules",

2. Basic Server​

const express = require("express");
const app = express();
const port = 3000;

app.get("/", (req, res) => {
  res.send("Hello World!");
});

app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});

Middlewares​

Using Middleware​

const express = require("express");
const app = express();

// Built-in middleware for parsing JSON
app.use(express.json());

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

Serving Static Files​

app.use(express.static("public"));

Routing​

Basic​

app.get("/", (req, res) => {
  res.send("GET request to the homepage");
});

app.post("/", (req, res) => {
  res.send("POST request to the homepage");
});

app.put("/user", (req, res) => {
  res.send("PUT request to /user");
});

app.delete("/user", (req, res) => {
  res.send("DELETE request to /user");
});

Route Parameters​

app.get("/users/:userId/books/:bookId", (req, res) => {
  res.send(req.params);
});

Query Strings​

app.get("/search", (req, res) => {
  res.send(req.query);
});

Handling Requests​

Request Object​

app.get("/user/:id", (req, res) => {
  console.log(req.params.id); // Route parameters
  console.log(req.query.name); // Query parameters
  console.log(req.body); // Request body (for POST/PUT requests)
});

Response Object​

app.get("/json", (req, res) => {
  res.json({ name: "Express" });
});

app.get("/status", (req, res) => {
  res.status(404).send("Not Found");
});

Advanced Topics​

Router​

const router = express.Router();

router.get("/", (req, res) => {
  res.send("Home page");
});

router.get("/about", (req, res) => {
  res.send("About page");
});

app.use("/pages", router);

Error Handling​

app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send("Something broke!");
});

Environment Variables​

const port = process.env.PORT || 3000;

Best practices

Using Template Engines​

Popular templates
app.set("view engine", "pug");
app.set("views", "./views");

app.get("/template", (req, res) => {
  res.render("index", { title: "Hey", message: "Hello there!" });
});

CORS​

const cors = require("cors");
app.use(cors());

Best Practices​

Environment Configuration​

require("dotenv").config();

// Note: Module JS using
// import dotenv from 'dotenv';
// dotenv.config();

const port = process.env.PORT || 3000;

Security​

const helmet = require("helmet");
app.use(helmet());

Logging​

const morgan = require("morgan");
app.use(morgan("combined"));