What is Node.js

• Environment to run JavaScript
  • Uses the Google v8 engine
  • Event Driven
  • Non-Blocking
  • Comes with API
• Good for I/O tasks
  • Web server for data
  • Chat/real-time social media server
• Not good for CPU tasks
  • Resizing photographs

Comparison Example

• Node vs PHP

//start_finish.js
var http = require('http');

http.createServer(function(request, response) {
  response.writeHead(200);
  response.write("Started.\n");
  setTimeout(function () {
    response.write("Finished.\n");
    response.end();
  }, 5000); 
}).listen(8000);

console.log('listening on port 8000...');

//start_finish.php
<?php

echo "Started";

sleep(5);

echo "Finished";

ab -r -n 1000 -c 1000 http://node
ab -r -n 1000 -c 1000 http://php

What Happened?

• Breakdown of the Apache vs Node Requests
• Node.js uses a single process
  • Event Loop
  • Blocking vs Non-Blocking
    • start_finish.js timeline comparrison blocking vs non-blocking

    var startTime = new Date().getTime();
    while (new Date().getTime() < startTime + 5000);

I/O Latency

• L1 CPU Cache: 3 CPU cycles
• L2 CPU Cache: 14 CPU cycles
• RAM: 250 CPU cycles
• DISK: 41,000,000 cycles
• NETWORK: 240,000,000 cycles

Create an App

• Creating a node app is easy… make a JavaScript file
  • Regular JavaScript syntax

//hello.js
var name = "World"
console.log("Hello " + name);

Node Globals

• Commonly used globals ¹
  • __filename - Absolute path to file executing the code
  • __dirname - Absolute path to directory the code is in
  • module - Reference to the current module
  • exports - Reference to module.exports used to provide
  • process - Work with the current running node process
    • process.argv - Get the argument vector
• And some familar
  • setTimeout(), setInterval(), clearInterval(), console()

Assignment 1 - Hello World!

• Remake the hello world app using process.argv