Programming
Express

Getting Started

Hello World {.row-span-2}

  • "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 {.row-span-2}

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()# (opens in a new tab)
express.raw()# (opens in a new tab)
express.Router()# (opens in a new tab)
express.static()# (opens in a new tab)
express.text()# (opens in a new tab)
express.urlencoded()# (opens in a new tab)

Router

:-:-
router.all()# (opens in a new tab)
router.METHOD()# (opens in a new tab)
router.param()# (opens in a new tab)
router.route()# (opens in a new tab)
router.use()# (opens in a new tab)

Application

var express = require('express')
var app = express()
 
console.dir(app.locals.title)
//=> 'My App'
console.dir(app.locals.email)
//=> 'me@myapp.com'

Attribute

:-:-
app.localsLocal variables in the application # (opens in a new tab)
app.mountpathPath pattern for mounting sub-apps # (opens in a new tab)

Events

:-:-
mountThe child application is mounted on the parent application, and the event is triggered on the child application # (opens in a new tab)

Method

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

Request

Attribute

:-:-
req.app# (opens in a new tab)
req.baseUrl# (opens in a new tab)
req.body# (opens in a new tab)
req.cookies# (opens in a new tab)
req.fresh# (opens in a new tab)
req.hostname# (opens in a new tab)
req.ip# (opens in a new tab)
req.ips# (opens in a new tab)
req.method# (opens in a new tab)
req.originalUrl# (opens in a new tab)
req.params# (opens in a new tab)
req.path# (opens in a new tab)
req.protocol# (opens in a new tab)
req.query# (opens in a new tab)
req.route# (opens in a new tab)
req.secure# (opens in a new tab)
req.signedCookies# (opens in a new tab)
req.stale# (opens in a new tab)
req.subdomains# (opens in a new tab)
req.xhr# (opens in a new tab)

Method

:-:-
req.accepts()# (opens in a new tab)
req.acceptsCharsets()# (opens in a new tab)
req.acceptsEncodings()# (opens in a new tab)
req.acceptsLanguages()# (opens in a new tab)
req.get()Get HTTP request header fields # (opens in a new tab)
req.is()# (opens in a new tab)
req.param()# (opens in a new tab)
req.range()# (opens in a new tab)

Response

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

Attribute

:-:-
res.app# (opens in a new tab)
res.headersSent# (opens in a new tab)
res.locals# (opens in a new tab)

Method

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

Example

Router {. row-span-2}

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!'
  })
})
SwiftC