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What is Express?

Learn what the Express framework is and how to install it.

What is Express?

Express is the most popular web framework for Node.js. It wraps the built-in http module and makes routing, request handling and sending responses easier. With Express you can set up a web server in a few lines.

Express is not built in; you install it with npm install express. Then you import it with const express = require("express");. Express is built on top of http.createServer, but it lets you write far less code. For example, defining a route is one line in Express, but an if-else chain in the raw http module. That is why most Node.js web projects start with Express.

Why Express?

Express simplifies many things compared to the http module. For routing you just write app.get("/path", handler); no if-else chain. For a JSON response res.json(data) is one line.

Express also gives middleware support: app.use(express.json()) automatically parses incoming JSON bodies. This is a task you do by hand in the http module. Express's simplicity makes it usable in projects of any size, from a small API to a large web app. In this group you will learn the core tools of Express: express(), app.get, app.post and app.listen.

Practice Import Express

Import the express module with require. Print "Express ready" with console.log.

Starter code

index.js
// Import the express module
// write here

// Print "Express ready"
// write here

Sample solution

index.js
const express = require("express");
console.log("Express ready");

Expected output

Express hazır

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 How is Express imported?

index.js
const express = require("express")
  • const express = require("http")
  • import express from "node"
  • const express = new Express()
  • const express = require("express") Correct answer

Explanation: Express is imported with require('express').

2 Complete the module name

Question 
const express = require("____");
Answer 
const express = require("express");

Explanation: The Express module is loaded as 'express'.

3 Match each piece to its role

Term Meaning
express Web framework
npm install Installs the module
require Imports the module
app Express application

All lessons in Intermediate

1 Events

  1. EventEmitter
  2. on and emit
  3. once
  4. removeListener
  5. error event
  6. Summary - Events

2 Streams

  1. What are streams?
  2. Readable stream
  3. Writable stream
  4. pipe
  5. Transform stream
  6. Summary - Streams

3 HTTP server

  1. http.createServer
  2. Request and response
  3. Routing
  4. JSON response
  5. Query string
  6. Summary - HTTP server

4 Project: Helper library

  1. Module design
  2. String helpers
  3. Number helpers
  4. Date helpers
  5. Putting it together

5 Express basics

  1. What is Express?
  2. express()
  3. app.get
  4. app.post
  5. app.listen
  6. Summary - Express basics

6 Middleware

  1. What is middleware?
  2. app.use
  3. Router middleware
  4. Error middleware
  5. Body parser
  6. Summary - Middleware

7 Routing

  1. Route parameters
  2. Query parameters
  3. express.Router
  4. Route groups
  5. Method chaining
  6. Summary - Routing

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Async patterns

  1. Async iteration
  2. Async generators
  3. Concurrency limit
  4. Retry pattern
  5. Debounce and throttle
  6. Summary - Async patterns

10 Buffer and binary

  1. What is Buffer?
  2. Buffer.from
  3. Buffer.concat
  4. toString and encoding
  5. Buffer slice
  6. Summary - Buffer

11 Process and CLI

  1. process.argv
  2. process.env
  3. process.exit
  4. process.stdin/stdout
  5. Child process
  6. Summary - Process

12 Project: Library API

  1. Model design
  2. Express app
  3. CRUD routes
  4. Middleware
  5. Putting it together

13 npm and packages

  1. npm install
  2. package.json scripts
  3. devDependencies
  4. Semver
  5. npm publish
  6. Summary - npm

14 Error handling

  1. The Error class
  2. try/catch
  3. Custom errors
  4. Error middleware
  5. Unhandled rejection
  6. Summary - Error handling

15 Testing basics

  1. node:test
  2. assert
  3. describe and it
  4. Before and after
  5. Mock
  6. Summary - Testing basics

16 Debugging

  1. node inspect
  2. Chrome DevTools
  3. console methods
  4. util.inspect
  5. Source maps
  6. Summary - Debugging

17 Date and time

  1. The Date object
  2. Date methods
  3. Intl.DateTimeFormat
  4. performance.now
  5. setTimeout and setInterval
  6. Summary - Date and time

18 Crypto

  1. crypto module
  2. createHash
  3. randomBytes
  4. HMAC
  5. AES
  6. Summary - Crypto

19 URL and query string

  1. URL object
  2. URLSearchParams
  3. URL properties
  4. URL.resolve
  5. querystring
  6. Summary - URL and query string

20 Intermediate final

  1. Project design
  2. Express API
  3. fs persistence
  4. Middleware
  5. Putting it together