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

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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);
//=> 'me@myapp.com'

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 {. 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!",
  });
});