Starting out with Express.js

Express.js is a simple and easy to use web framework for coding and building the web using node.js. The easiest way to get started is by install the command line tool express-generator.

Building the express.js application

You can install it by running npm:

$ npm install -g express-generator

Then go into your project directory (e.g ~/Sites) and build your project with the generator:

$ express sample-file
$ cd sample-file # change current directory to file just created
$ npm install # install dependencies
$ npm start # start node app

Understanding the code

Once you have a running application, open up the routes folder and go to index.js. This is the file that identifies all the routes. The file should look like this:

var express = require("express");
var router = express.Router();
/* GET home page. */
router.get("/", function (req, res, next) {
	res.render("index", { title: "Express" });
});
module.exports = router;

If you go to localhost:3000 in your browser you should notice that the title is named “Express”. This is res.render in action, he will find the view for the function and use a templating engine (handlebars.js, embedded.js, and jade) to make your application pass information between the client and the server. There are many other ways of accomplishing this, but this way is the most easy and fun way to learn back-end java-scripting.

Making your app pass info from the server

You can easily make your server pass data to the client. Let’s say you want to get the date when the server returned the user’s request, simply pass a

Date constructor and you are set:

var express = require("express");
var router = express.Router();
/* GET home page. */
router.get("/", function (req, res, next) {
	res.render("index", { title: new Date() });
});
module.exports = router;

Making your app pass data to the server

In your views directory, find index.jade and create a form:

extends layout

block content
  h1= title
  p Welcome to #{title}

  h2 update title
  form(name="/", method="post")
    input(type="text", name="title" placeholder="title")
    input(type="submit", value="go")

Then in index.js, add a new method to the router, called POST:

var express = require("express");
var router = express.Router();

/* GET home page. */
router.get("/", function (req, res, next) {
	res.render("index", { title: new Date() });
});

/* POST home page. */
router.post("/", function (req, res) {
	res.render("index", { title: req.body.title });
});

module.exports = router;