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Express

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

#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

#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

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!",
  });
});