Introduction to Wed Dev

Client-Server Architecture

Internet

Server

Client

HTTP

Hypertext Transfer Protocol
The protocol to exchange or transfer hypertext
E.g. a client requests a webpage from a server using a HTTP request

HTTP Methods

GET
DELETE
PUT
POST

GET /index.html HTTP/1.1
Host: www.example.com

HTTP/1.1 200 OK
Date: Mon, 1 Jan 2015 22:38:34 GMT
Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 31 Dec 2014 23:11:55 GMT
ETag: "3f80f-1b6-3e1cb03b"
Content-Type: text/html; charset=UTF-8
Content-Length: 131
Accept-Ranges: bytes
Connection: close

<html>
<head>
  <title>An Example Page</title>
</head>
<body>
  Hello World
</body>
</html>

Client Request

Server Response

Status Codes

200 OK
304 Not Modified
403 Forbidden
404 Not Found
500 Internal Server Error

Node.js

Runtime Environment
Runs on Windows, Mac OS X, Linux
Node.js applications are written in Javascript
Javascript is executed using Google V8 JS engine
V8 is written in C++ (very fast)
Single-threaded
Non-blocking IO

Non-blocking IO

Blocking Code

function exponentiate(base, index) {
    var ans = base;
    for (var i=1; i<index; i++) {
        ans = ans * base;
    }
    return ans;
}

console.log(exponentiate(10, 6));

console.log("Hello World");

Non-Blocking Code with callbacks

function exponentiate(base, index, cb) {
    var ans = base;
    for (var i=1; i<index; i++) {
        ans = ans * base;
    }
    cb(ans);
}

exponentiate(10, 6, function callback(ans) {
    console.log(ans);
});

console.log("Hello World");

Non-blocking code allows for highly concurrent applications, allowing support for tens of thousands of concurrent connecions

NPM

Node Package Manager
Useful frameworks and libraries
npmjs.com

Practise Time

Install Node.JS (nodejs.org)
Go to nodeschool.io