Introduction to NodeJS/ExpressJS

Chandan Jhunjhunwal

Session -1

13/01/2017

Basics

• V8 Engine
• Sync vs Async functions
• Understanding call stacks
• Web APIs and Task queues
• http://latentflip.com/loupe/
• https://jsfiddle.net/dkdk5y8a/1/
• Why setTimeout(fn(), 0)?

Async Call

NodeJS

• NPM
• NVM
• package.json
• Built in modules
• Third party modules
• Your own module

var url = require("url");

var parsedURL = url.parse("http://www.example.com/profile?name=barry");

console.log(parsedURL.protocol);  // "http:"
console.log(parsedURL.host);      // "www.example.com"
console.log(parsedURL.query);     // "name=barry"

Built in module

Mustache.render("Hello, {{first}} {{last}}!", {
  first: "Nicolas",
  last: "Cage"
});


Mustache.render("Hello, {{first}} {{last}}!", {
  first: "Sheryl",
  last: "Sandberg"
});

Third Party Module

var MAX = 100;

function randomInteger() {
  return Math.floor((Math.random() * MAX));
}

module.exports = randomInteger;

Your module

1. Find number of 'X' (case insensitive) in a text file from disc 
   using file system 'fs' module.

2. Write console.log at the end of file, check what's gets 
   printed first

Async Calls

var http = require("http");

function requestHandler(request, response) {
  console.log("In comes a request to: " + request.url);
  response.end("Hello, world!");
}

var server = http.createServer(requestHandler);

server.listen(3000);

http server

Node vs Express

Node JS

ExpressJS

// Node http server
var http = require("http");

requestHandler = function(req, res){
  if(req.url === '/'){
        res.end('Home page')
    }
  else {
     res.end("Don't go out of home");   
  }
}

var server = http.createServer(requestHandler);

server.listen(3000)


// Express Server
var express = require('express');

var funApp = express();

funApp.get('/', function(req, res){
  console.log("request received at" + req.url);
  response.send("Hello world!");
})

fundApp.listen(3000, function(){
  console.log('Application Started...');
})

References

• Google
• Stackoverflow
• Event Loop: JSConf EU 2014(Philip Roberts talk)
• ExpressJS in Action

Thank You!