w3_d3_1_express_continued

#Node Continued

##JavaScript Runtime

• Node operates on the V8 Google Chrome JavaScript runtime.
• This runtime is what is responsible for interpreting the JavaScript and mapping it over to machine commands.
• Commands are executed through an architecture known as the "call stack." Currently-processing requests are part of the call stack, and come from the process queue.

##What is Node?

• Node JS is an interface that allows you to write server-side code in JavaScript.
• This interface provides the ability to handle requests and issue responses.
• It is asynchronous, and as a result, can be written in a way that will not block the call stack.
• Node is also a server that will allow your code to be accessible to the public and be able to issue responses for certain requests.

##First Server with Node

// server.js
var http = require("http");

function greet(req, res) {
	res.writeHead(200, {"Content-Type": "text/plain"});
	res.write("Hello World");
	res.end();
}

var server = http.createServer(greet);

server.listen(3000);

##Express JS

• Express is an API to Node JS that makes development more intuitive and quicker.
• Express allows us to easily set up routes that will trigger actions such as rendering pages.

##NPM and NPM Init

• NPM stands for Node Package Manager, and is a tool that allows us to easily download community-built Node packages.
• Initialize new Node project with NPM: npm init
• Install NPM packages: npm install --save express
• NPM works with package.json, which is a list of dependencies that can be installed on other computers and servers.

##Hello World in Node

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World!');
})

var server = app.listen(3000);

##What is Node Good For?

• Node really shines when it comes to heavy input-output type operations.
• Realtime services like chat applications or conferencing platforms benefit from using Node.
• APIs are also input/output heavy, and they also tend to work with JavaScript out of the box (think JSON). What better platform than Node?

##An API Application with Node

• We will be building in class today a Node application that sends and receives JSON.
• We will try to replicate relatively the same functionality as http://daretodiscover.herokuapp.com/users.
• Here are the steps we will follow:
  • Step 1: Set up a brand new Node project using NPM.
  • Step 2: Install relevant NPM modules for your project (Express and Body Parser).
  • Step 3: Create a blank array called users that will hold all of the user objects.
  • Step 4: Create the route GET /users. It should send back the users array as JSON.
  • Step 5: Create the route GET /users/:id that has an ID parameter that will send back a JSON response of a particular user based on their ID.
  • Step 6: Create the route POST /users. It should add a new user object to the array users.
  • Step 7: Use Postman to test each of these routes.