Express CHEAT SHEET

A quick reference cheatsheet for Express, a flexible and streamlined web framework for Node.js

configformat

Sections

Cards

#Getting Started

Hello World

"Create project, add package.json configuration

$ mkdir myapp # create directory
$ cd myapp    # enter the directory
$ npm init -y # Initialize a configuration

Install dependencies
```
$ npm install express
```

Entry file index.js add code:

const express = require('express');
const app = express();
const port = 3000;
app.get('/', (req, res) => {
  res.send('Hello World!');
});
app.listen(port, () => {
  console.log(`Listening port on ${port}`);
});

Run the application using the following command
```
$ node index.js
```
{.marker-timeline}

express -h

Usage: express [options] [dir]
Options:
  -h, --help output usage information
      --version output version number
  -e, --ejs add ejs engine support
      --hbs add hbs engine support
      --pug add pug engine support
  -H, --hogan add hogan.js engine support
      --no-view No view engine generated
  -v, --view <engine> add view <engine> support (ejs|hbs|hjs|jade|pug|twig|vash) (default jade)
  -c, --css <engine> add stylesheet <engine> support (less|stylus|compass|sass) (default css)
      --git add .gitignore
  -f, --force force non-empty directories

{.wrap-text}

Create a myapp project

$ express --view=pug myapp
# run the application
$ DEBUG=myapp:*npm start

express()

:-	:-
`express.json()`	#
`express.raw()`	#
`express.Router()`	#
`express.static()`	#
`express.text()`	#
`express.urlencoded()`	#

Router

:-	:-
`router.all()`	#
`router.METHOD()`	#
`router.param()`	#
`router.route()`	#
`router.use()`	#

Application

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

console.dir(app.locals.title);
//=> 'My App'
console.dir(app.locals.email);
//=> '[email protected]'

Attribute

:-	:-
`app.locals`	Local variables in the application #
`app.mountpath`	Path pattern for mounting sub-apps #

Events

:-	:-
`mount`	The child application is mounted on the parent application, and the event is triggered on the child application #

Method

:-	:-
`app.all()`	#
`app.delete()`	#
`app.disable()`	#
`app.disabled()`	#
`app.enable()`	#
`app.enabled()`	#
`app.engine()`	#
`app.get(name)`	#
`app.get(path, callback)`	#
`app.listen()`	#
`app.METHOD()`	#
`app.param()`	#
`app.path()`	#
`app.post()`	#
`app.put()`	#
`app.render()`	#
`app.route()`	#
`app.set()`	#
`app.use()`	#

Request

Attribute

:-	:-
`req.app`	#
`req.baseUrl`	#
`req.body`	#
`req.cookies`	#
`req.fresh`	#
`req.hostname`	#
`req.ip`	#
`req.ips`	#
`req.method`	#
`req.originalUrl`	#
`req.params`	#
`req.path`	#
`req.protocol`	#
`req.query`	#
`req.route`	#
`req.secure`	#
`req.signedCookies`	#
`req.stale`	#
`req.subdomains`	#
`req.xhr`	#

Method

:-	:-
`req.accepts()`	#
`req.acceptsCharsets()`	#
`req.acceptsEncodings()`	#
`req.acceptsLanguages()`	#
`req.get()`	Get HTTP request header fields #
`req.is()`	#
`req.param()`	#
`req.range()`	#

Response

app.get('/', function (req, res) {
  console.dir(res.headersSent); //false
  res.send('OK');
  console.dir(res.headersSent); //true
});

Attribute

:-	:-
`res.app`	#
`res.headersSent`	#
`res.locals`	#

Method

:-	:-
`res.append()`	#
`res.attachment()`	#
`res.cookie()`	#
`res.clearCookie()`	#
`res.download()`	Prompt for files to download #
`res.end()`	end the response process #
`res.format()`	#
`res.get()`	#
`res.json()`	Send JSON response #
`res.jsonp()`	Send a response with JSONP support #
`res.links()`	#
`res.location()`	#
`res.redirect()`	Redirect request #
`res.render()`	render view template #
`res.send()`	Send various types of responses #
`res.sendFile()`	Send a file as an octet stream #
`res.sendStatus()`	#
`res.set()`	#
`res.status()`	#
`res.type()`	#
`res.vary()`	#

#Example

Router

Called for any request passed to this router

router.use(function (req, res, next) {
  //.. some logic here .. like any other middleware
  next();
});

will handle any request ending in /events

//depends on where the router "use()"
router.get('/events', (req, res, next) => {
  //..
});

Response

The res object represents the HTTP response sent by the Express application when it receives an HTTP request

app.get('/user/:id', (req, res) => {
  res.send('user' + req.params.id);
});

Request

A req object represents an HTTP request and has properties for the request query string, parameters, body, HTTP headers, etc.

app.get('/user/:id', (req, res) => {
  res.send('user' + req.params.id);
});

res. end()

res.end();
res.status(404).end();

End the response process. This method actually comes from the Node core, specifically the response.end() method of http.ServerResponse

res.json([body])

res.json(null);
res.json({ user: 'tobi' });
res.status(500).json({ error: 'message' });

app.all

app.all('/secret', function (req, res, next) {
  console.log('access secret section...');
  next(); // Pass control to the next handler
});

app.delete

app.delete('/', function (req, res) {
  res.send('DELETE request to homepage');
});

app.disable(name)

app.disable('trust proxy');
app.get('trust proxy');
// => false

app.disabled(name)

app.disabled('trust proxy');
// => true

app.enable('trust proxy');
app.disabled('trust proxy');
// => false

app.engine(ext, callback)

var engines = require('consolidate');

app.engine('haml', engines.haml);
app.engine('html', engines.hogan);

app.listen([port[, host[, backlog]]][, callback])

var express = require('express');

var app = express();
app.listen(3000);

Routing

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

//Respond to "hello world" when making a GET request to the homepage
app.get('/', (req, res) => {
  res.send('hello world');
});

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

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

Middleware

function logOriginalUrl(req, res, next) {
  console.log('ReqURL:', req.originalUrl);
  next();
}

function logMethod(req, res, next) {
  console.log('Request Type:', req.method);
  next();
}

const log = [logOriginalUrl, logMethod];

app.get('/user/:id', log, (req, res, next) => {
  res.send('User Info');
});

Using templates

app.set('view engine', 'pug');

Create a Pug template file named index.pug in the views directory with the following content

html
  the head
    title= title
  the body
    h1=message

Create a route to render the index.pug file. If the view engine property is not set, the extension of the view file must be specified

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