What is Node.js?

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Simple Server

Executes JavaScript
Event Driven Concurrency
Emits Events
Listens for Responses

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Node.js is NOT:

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NOT written in JS
- IS a C based interpreter running the V8 JS engine
NOT a framework, more like an API
NOT multi-threaded
- IS single threaded, using events and callbacks

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Pros and Cons

Node.js

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Pros

Write JS on client and Server
Fast executions (Node is written in C and uses V8, which is also C)
Asynchronous executions
NPM allows for easy module sharing (like Ruby Gems)
Great for running development build tasks

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Cons

Very low-level JS
Can be problematic at scale (single threaded)
Callback execution flow can be hard to master

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Getting Started

$ git clone https://github.com/rileyhilliard/usc-lecture.git usc-node-demo

$ cd usc-node-demo/node-server

nodejs.org

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Hello World: I

// server.js

console.log('Helo World!');
console.log('This was logged from the node.js server');

$ node server.js

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Hello World: II

$ node hello.js

Node.js is a webserver with an API
Loading a module allows the use of it's methods
node.js http docs: nodejs.org/api/http.html

HTTP Module

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

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  console.log("I am going to write 'Hello World'");
  res.end('Hello World\n');
  console.log("I wrote 'Hello World'");
}).listen(3000);

console.log('Server running at http://localhost:3000/');

Async Call Stack

$ node async.js

Callbacks can be confusing
'seconds()' function runs async
'http.createServer()' fires on page visit

// async.js
var http = require('http');
var counter = 0;

var isThisLast = function(message){
  console.log('3 - isThisLast\'s message is: '+message);
};

var doThisFunction = function(res, func){
  setTimeout(function(){
    console.log('4 - doing doThisFunction');
  },3000)
  func("What's Up Last function being called?!");
};

var seconds = function(){
  var seconds = 0;
  var plural = "";
  setInterval(function(){
    seconds++;
    plural = (seconds > 1 ? "s" : "");
    console.log("It's been "+seconds+" second"+plural+"\n");
  },1000)
};

var doAnotherThing = function(res){
  console.log('2 - doing ANOTHER thing');
  doThisFunction(res, isThisLast);
};

http.createServer(function (req, res) {
  counter++;
  res.writeHead(200, {'Content-Type': 'text/plain'});
  setTimeout(function(){
    doAnotherThing(res);
  }, 0);
  console.log('1 - == END OF STACK == Ran this thing '+counter+' times')
  res.end('Hello World\n');
}).listen(3000);

seconds();
console.log('Server running at http://localhost:3000/');

Write to File

$ node file.js

fs = node File System module
File read/write helper

//file.js
var http = require('http');
var fs = require('fs');
var message = "This is the Message that is going";
message += "to be written to a file";

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  fs.writeFile("test.txt", message, function(err) {
    if(err) {
      res.end(err);
    } else {
      console.log("The file was saved!");
      res.end('The file was saved!\n');
    }
  });
}).listen(3000);

console.log('Server running at http://localhost:3000/');

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