Express

https://expressjs.com/
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Express is a fast, unopinionated, minimalist web framework for Node.js that provides a robust set of...
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### Debug output for app startup

Source: https://expressjs.com/en/5x/guide/debugging/

Example output from running the sample app with DEBUG enabled, showing Express configuration and router setup logs.

```text
$ DEBUG=express:*,router,router:* node index.js
  express:application set "x-powered-by" to true +0ms
  express:application set "etag" to 'weak' +3ms
  express:application set "etag fn" to [Function: generateETag] +0ms
  express:application set "env" to 'development' +1ms
  express:application set "query parser" to 'simple' +0ms
  express:application set "query parser fn" to [Function: parse] +0ms
  express:application set "subdomain offset" to 2 +1ms
  express:application set "trust proxy" to false +0ms
  express:application set "trust proxy fn" to [Function: trustNone] +1ms
  express:application booting in development mode +0ms
  express:application set "view" to [Function: View] +0ms
  express:application set "views" to '/projects/example/views' +1ms
  express:application set "jsonp callback name" to 'callback' +0ms
  router use '/' jsonParser +0ms
  router:layer new '/' +0ms
  router:route new '/' +0ms
  router:layer new '/' +3ms
  router:route get / +0ms
  router:layer new '/' +1ms
  router use '/users' router +4ms
  router:layer new '/users' +0ms
  router:route new '/' +1ms
  router:layer new '/' +0ms
  router:route get / +1ms
  router:layer new '/' +1ms
```

--------------------------------

### Install serve-static with bun

Source: https://expressjs.com/en/resources/middleware/serve-static/

Install the serve-static middleware using bun.

```bash
bun add serve-static
```

--------------------------------

### Install morgan with yarn

Source: https://expressjs.com/en/resources/middleware/morgan/

Install morgan using yarn.

```bash
yarn add morgan
```

--------------------------------

### Install morgan with bun

Source: https://expressjs.com/en/resources/middleware/morgan/

Install morgan using bun.

```bash
bun add morgan
```

--------------------------------

### Run the app with node app.js

Source: https://expressjs.com/en/4x/starter/hello-world/

Command to start the Express server. Run in the myapp directory after creating app.js with the example code. Then visit http://localhost:3000/.

```bash
$ node app.js
```

--------------------------------

### Install morgan with npm

Source: https://expressjs.com/en/resources/middleware/morgan/

Install morgan using npm.

```bash
npm install morgan
```

--------------------------------

### req.hostname example

Source: https://expressjs.com/en/4x/api/request/

Shows how to get the hostname from the Host header using req.hostname. Outputs 'example.com'.

```javascript
// Host: "example.com:3000"
console.dir(req.hostname);
// => 'example.com'
```

--------------------------------

### app.path() example (JavaScript)

Source: https://expressjs.com/en/4x/api/application/

Shows how to use app.path() to get the canonical path of an app. Creates a main app and two mounted sub-apps, then logs their paths: '' for the main app, '/blog' for the blog app, and '/blog/admin' for the blogAdmin app.

```javascript
var app = express();
var blog = express();
var blogAdmin = express();

app.use('/blog', blog);
blog.use('/admin', blogAdmin);

console.dir(app.path()); // ''
console.dir(blog.path()); // '/blog'
console.dir(blogAdmin.path()); // '/blog/admin'
```

--------------------------------

### Install morgan with pnpm

Source: https://expressjs.com/en/resources/middleware/morgan/

Install morgan using pnpm.

```bash
pnpm add morgan
```

--------------------------------

### Install connect-timeout with bun

Source: https://expressjs.com/en/resources/middleware/timeout/

Install the connect-timeout middleware using bun.

```bash
bun add connect-timeout
```

--------------------------------

### Install serve-favicon with bun

Source: https://expressjs.com/en/resources/middleware/serve-favicon/

Install the serve-favicon package using bun.

```bash
bun add serve-favicon
```

--------------------------------

### Install response-time with bun

Source: https://expressjs.com/en/resources/middleware/response-time/

Install the response-time middleware using bun.

```bash
bun add response-time
```

--------------------------------

### Install response-time with pnpm

Source: https://expressjs.com/en/resources/middleware/response-time/

Install the response-time middleware using pnpm.

```bash
pnpm add response-time
```

--------------------------------

### Install connect-timeout with npm

Source: https://expressjs.com/en/resources/middleware/timeout/

Install the connect-timeout middleware using npm.

```bash
npm install connect-timeout
```

--------------------------------

### Install serve-favicon with yarn

Source: https://expressjs.com/en/resources/middleware/serve-favicon/

Install the serve-favicon package using yarn.

```bash
yarn add serve-favicon
```

--------------------------------

### Output for GET /user/42/3 with array param

Source: https://expressjs.com/en/4x/api/application/

Expected console output when requesting GET /user/42/3 with the array-parameter example.

```plaintext
CALLED ONLY ONCE with 42
CALLED ONLY ONCE with 3
although this matches
and this matches too
```

--------------------------------

### Initialize package.json with bun

Source: https://expressjs.com/en/4x/starter/installing/

Runs 'bun init' to create a package.json file. Prompts for project details; press RETURN to accept defaults.

```bash
bun init
```

--------------------------------

### Define GET and POST routes (JavaScript)

Source: https://expressjs.com/en/4x/guide/routing/

Example of defining GET and POST routes to the root of the app. The GET route responds with 'GET request to the homepage', and the POST route responds with 'POST request to the homepage'.

```JavaScript
// GET method route
app.get('/', (req, res) => {
  res.send('GET request to the homepage');
});

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

--------------------------------

### Create and navigate to application directory

Source: https://expressjs.com/en/4x/starter/installing/

Creates a directory named 'myapp' and navigates into it. Required before initializing the project.

```bash
mkdir myapp
cd myapp
```

--------------------------------

### Start the Express 4 app

Source: https://expressjs.com/en/guide/migrating-4/

After installing dependencies, run this command to start the app. The npm start script runs node ./bin/www, which used to be node app.js in Express 3.

```bash
$ npm start
```

--------------------------------

### Define GET and POST routes (TypeScript)

Source: https://expressjs.com/en/4x/guide/routing/

TypeScript version of the GET and POST route examples, with type annotations for Request and Response.

```TypeScript
import { type Request, type Response } from 'express';

// GET method route
app.get('/', (req: Request, res: Response) => {
  res.send('GET request to the homepage');
});

// POST method route
app.post('/', (req: Request, res: Response) => {
  res.send('POST request to the homepage');
});
```

--------------------------------

### Install serve-index with bun

Source: https://expressjs.com/en/resources/middleware/serve-index/

Install the serve-index middleware using bun.

```bash
bun add serve-index
```

--------------------------------

### Initialize package.json with npm

Source: https://expressjs.com/en/4x/starter/installing/

Runs 'npm init' to create a package.json file. Prompts for project details; press RETURN to accept defaults.

```bash
npm init
```

--------------------------------

### req.route example (JavaScript and TypeScript)

Source: https://expressjs.com/en/5x/api/request/

Shows how to access the currently-matched route object. The example logs the route with depth null and sends 'GET'.

```javascript
app.get('/user/{:id}', (req, res) => {
  console.dir(req.route, { depth: null });
  res.send('GET');
});
```

```typescript
import { type Request, type Response } from 'express';

app.get('/user/{:id}', (req: Request, res: Response) => {
  console.dir(req.route, { depth: null });
  res.send('GET');
});
```

--------------------------------

### app.get(path, callback) - Route HTTP GET Requests

Source: https://expressjs.com/en/4x/api/application/

Routes HTTP GET requests to the specified path with the given callback function. This is an example of app.METHOD routing.

```APIDOC
## app.get(path, callback) - Route HTTP GET Requests

### Description
Routes HTTP GET requests to the specified path with the given callback function. This is an example of app.METHOD routing.

### Method
GET

### Endpoint
`path` (string) - The path for which the middleware function is invoked.

### Parameters
#### Path Parameters
- **path** (string) - Required - The path for which the middleware function is invoked.

#### Request Body
- **callback** (function) - Required - Callback function that handles the request and response.

### Request Example
```javascript
app.get('/', function (req, res) {
  res.send('hello world');
});
```

### Response
#### Success Response (200)
- **res** (Response) - The response object used to send data back to the client.

#### Response Example
```javascript
res.send('hello world');
```
```

--------------------------------

### app.get(name) - Get setting value

Source: https://expressjs.com/en/3x/api/application/

Gets the value of setting 'name'. The example shows that before setting, app.get('title') returns undefined; after setting, it returns 'My Site'.

```javascript
app.get('title');
// => undefined

app.set('title', 'My Site');
app.get('title');
// => "My Site"
```

--------------------------------

### req.params named parameter example

Source: https://expressjs.com/en/3x/api/request/

Shows how to access a named route parameter via req.params.name. For the route /user/:name, the example outputs the value 'tj' for a GET request to /user/tj.

```javascript
// GET /user/tj
console.dir(req.params.name);
// => 'tj'
```

--------------------------------

### Install serve-static with pnpm

Source: https://expressjs.com/en/resources/middleware/serve-static/

Install the serve-static middleware using pnpm.

```bash
pnpm add serve-static
```

--------------------------------

### Using vhost with Connect for static serving

Source: https://expressjs.com/en/resources/middleware/vhost/

Sets up a Connect app that routes mail.example.com to a mail app and assets-*.example.com to a static file server. The static app serves files from the 'public' directory. This example shows how to use wildcard subdomains to work around browser host connection limits.

```javascript
var connect = require('connect');
var serveStatic = require('serve-static');
var vhost = require('vhost');

var mailapp = connect();

// add middlewares to mailapp for mail.example.com

// create app to serve static files on subdomain
var staticapp = connect();
staticapp.use(serveStatic('public'));

// create main app
var app = connect();

// add vhost routing to main app for mail
app.use(vhost('mail.example.com', mailapp));

// route static assets for "assets-*" subdomain to get
// around max host connections limit on browsers
app.use(vhost('assets-*.example.com', staticapp));

// add middlewares and main usage to app

app.listen(3000);
```

--------------------------------

### req.originalUrl example

Source: https://expressjs.com/en/3x/api/request/

Shows that req.originalUrl retains the original request URL even if req.url is rewritten for internal routing. The example outputs the original URL for a GET request to /search?q=something.

```javascript
// GET /search?q=something
console.log(req.originalUrl);
// => "/search?q=something"
```

--------------------------------

### req.originalUrl: basic example

Source: https://expressjs.com/en/4x/api/request/

Logs the original request URL for a GET request to /search?q=something.

```javascript
// GET /search?q=something
console.dir(req.originalUrl);
// => '/search?q=something'
```

--------------------------------

### Minimal Express web server example

Source: https://expressjs.com/

This is the classic 'Hello World' example for Express. It creates an app that listens on port 3000 and responds with 'Hello World!' at the root route. Requires Express to be installed.

```javascript
const express = require('express');
const app = express()
const port = 3000

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

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})
```

--------------------------------

### Install serve-index with pnpm

Source: https://expressjs.com/en/resources/middleware/serve-index/

Install the serve-index middleware using pnpm.

```bash
pnpm add serve-index
```

--------------------------------

### Initialize package.json with pnpm

Source: https://expressjs.com/en/4x/starter/installing/

Runs 'pnpm init' to create a package.json file. Prompts for project details; press RETURN to accept defaults.

```bash
pnpm init
```

--------------------------------

### req.params capture group example

Source: https://expressjs.com/en/3x/api/request/

Shows how capture groups from regular expression routes or unnamed wild-card matches are accessed via req.params[N]. The example outputs the captured path segment for a GET request to /file/javascripts/jquery.js.

```javascript
// GET /file/javascripts/jquery.js
console.dir(req.params[0]);
// => 'javascripts/jquery.js'
```

--------------------------------

### app.on('mount') event example (JavaScript)

Source: https://expressjs.com/en/4x/api/application/

Shows how to listen for the 'mount' event on a sub-app. The callback receives the parent app. The sub-app is then mounted on the parent with app.use().

```JavaScript
var admin = express();

admin.on('mount', function (parent) {
  console.log('Admin Mounted');
  console.log(parent); // refers to the parent app
});

admin.get('/', function (req, res) {
  res.send('Admin Homepage');
});

app.use('/admin', admin);
```

--------------------------------

### app.get() example in JavaScript

Source: https://expressjs.com/en/5x/api/application/

Routes HTTP GET requests to the homepage path. The callback sends a response using res.send().

```JavaScript
app.get('/', (req, res) => {
  res.send('GET request to homepage');
});
```

--------------------------------

### req.subdomains example

Source: https://expressjs.com/en/5x/api/request/

Shows how to get the subdomains array from the Host header. The comment shows the Host and the output is the array of subdomains.

```javascript
// Host: "tobi.ferrets.example.com"
console.dir(req.subdomains);
// => ["ferrets", "tobi"]
```

--------------------------------

### Install serve-index with yarn

Source: https://expressjs.com/en/resources/middleware/serve-index/

Install the serve-index middleware using yarn.

```bash
yarn add serve-index
```

--------------------------------

### Optional segment with dot extension (JavaScript)

Source: https://expressjs.com/en/5x/guide/routing/

Defines a route where the extension is optional. When the segment is absent, the parameter is omitted from req.params. Example: GET /image.png yields { file: 'image', ext: 'png' }, GET /image yields { file: 'image' }.

```JavaScript
app.get('/:file{.:ext}', (req, res) => {
  // GET /image.png => req.params = { file: 'image', ext: 'png' }
  // GET /image => req.params = { file: 'image' }
  res.send('ok');
});
```

--------------------------------

### Equivalent app.all() calls for authentication and user loading

Source: https://expressjs.com/en/5x/api/application/

Shows the equivalent of the previous example by splitting the middleware into two separate app.all() calls, both using the '{*splat}' pattern.

```JavaScript
app.all('{*splat}', requireAuthentication);
app.all('{*splat}', loadUser);
```

--------------------------------

### Install couchbase with bun

Source: https://expressjs.com/en/guide/database-integration/

Install the Couchbase Node.js SDK using bun.

```bash
bun add couchbase
```

--------------------------------

### Wildcard parameter array with req.params.file (JavaScript)

Source: https://expressjs.com/en/5x/api/request/

Demonstrates that wildcard parameters are arrays of path segments split on '/'. For route /files/*file, req.params.file contains an array of segments. The example shows outputs for GET /files/note.txt and GET /files/images/image.png.

```JavaScript
app.get('/files/*file', (req, res) => {
  console.dir(req.params.file);
  // GET /files/note.txt
  // => [ 'note.txt' ]
  // GET /files/images/image.png
  // => [ 'images', 'image.png' ]
});
```

--------------------------------

### LevelDB example with levelup (CommonJS)

Source: https://expressjs.com/en/guide/database-integration/

Uses levelup to create a database, put a key-value pair, and get it back. The database is stored in './mydb'.

```javascript
const levelup = require('levelup');
const db = levelup('./mydb');

db.put('name', 'LevelUP', (err) => {
  if (err) return console.log('Ooops!', err);

  db.get('name', (err, value) => {
    if (err) return console.log('Ooops!', err);

    console.log(`name=${value}`);
  });
});
```

--------------------------------

### Install serve-static with yarn

Source: https://expressjs.com/en/resources/middleware/serve-static/

Install the serve-static middleware using yarn.

```bash
yarn add serve-static
```

--------------------------------

### Install serve-static with npm

Source: https://expressjs.com/en/resources/middleware/serve-static/

Install the serve-static middleware using npm.

```bash
npm install serve-static
```

--------------------------------

### Path example: exact path '/abcd' (JavaScript)

Source: https://expressjs.com/en/5x/api/application/

Mounts middleware on the path '/abcd', matching the exact path and any sub-paths starting with '/abcd/'.

```javascript
app.use('/abcd', (req, res, next) => {
  next();
});
```

--------------------------------

### Create Express app and define a route

Source: https://expressjs.com/en/3x/api/application/

Shows how to create an Express application, define a GET route, and start the server on port 3000.

```javascript
var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('hello world');
});

app.listen(3000);
```

--------------------------------

### Install cassandra-driver with bun

Source: https://expressjs.com/en/guide/database-integration/

Install the Cassandra driver for Node.js using bun.

```bash
bun add cassandra-driver
```

--------------------------------

### Install redis with bun

Source: https://expressjs.com/en/guide/database-integration/

Install the redis module using bun.

```bash
bun add redis
```

--------------------------------

### Install compression with bun

Source: https://expressjs.com/en/resources/middleware/compression/

Install the compression middleware using bun.

```bash
bun add compression
```

--------------------------------

### req.get(field) usage examples

Source: https://expressjs.com/en/3x/api/request/

Shows how to get a case-insensitive request header field. The 'Referrer' and 'Referer' fields are interchangeable. Returns undefined if the header is not present.

```javascript
req.get('Content-Type');
// => "text/plain"

req.get('content-type');
// => "text/plain"

req.get('Something');
// => undefined
```

--------------------------------

### Install serve-index with npm

Source: https://expressjs.com/en/resources/middleware/serve-index/

Install the serve-index middleware using npm.

```bash
npm install serve-index
```

--------------------------------

### LevelDB example with levelup (ESM)

Source: https://expressjs.com/en/guide/database-integration/

Uses levelup with ES module imports to create a database, put a key-value pair, and get it back. The database is stored in './mydb'.

```javascript
import levelup from 'levelup';

const db = levelup('./mydb');

db.put('name', 'LevelUP', (err) => {
  if (err) return console.log('Ooops!', err);

  db.get('name', (err, value) => {
    if (err) return console.log('Ooops!', err);

    console.log(`name=${value}`);
  });
});
```

--------------------------------

### Get req.host from Host header

Source: https://expressjs.com/en/5x/api/request/

Contains the host derived from the Host HTTP header. When trust proxy is enabled, uses X-Forwarded-Host. Shows examples with port and IPv6.

```javascript
// Host: "example.com:3000"
console.dir(req.host);
// => 'example.com:3000'

// Host: "[::1]:3000"
console.dir(req.host);
// => '[::1]:3000'
```

--------------------------------

### JavaScript wildcard route: /files/*filepath

Source: https://expressjs.com/en/5x/guide/routing/

Defines a wildcard route that captures any path after the prefix as an array of segments. The example shows req.params.filepath as ['images', 'logo.png'] for GET /files/images/logo.png.

```javascript
app.get('/files/*filepath', (req, res) => {
  // GET /files/images/logo.png
  console.dir(req.params.filepath);
  // => [ 'images', 'logo.png' ]
  res.send(`File: ${req.params.filepath.join('/')}`);
});
```

--------------------------------

### Basic route example in ESM (index.mjs)

Source: https://expressjs.com/en/4x/guide/routing/

Defines a basic GET route for the homepage using app.get() and sends 'hello world'. Uses ES module import syntax.

```javascript
import express from 'express';

const app = express();

// respond with "hello world" when a GET request is made to the homepage
app.get('/', (req, res) => {
  res.send('hello world');
});
```

--------------------------------

### app.set(name, value) - Set setting and get value

Source: https://expressjs.com/en/3x/api/application/

Assigns setting 'name' to 'value'. The example sets 'title' to 'My Site' and then retrieves it with app.get, which returns 'My Site'.

```javascript
app.set('title', 'My Site');
app.get('title');
// => "My Site"
```
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