1. RESTful Web Development With Nodejs and Express

2. REST • Stands for REpresentational State Transfer • Has the following constraints: • Client-Server • Stateless • Cacheable • Layered System • Code on Demand • Uniform Interface

3. REST on the web • Every kind of resource you want is at a different URI • Interact with resources using the HTTP verbs • PUT (Create) • GET (Read) • POST (Update) • DELETE (Delete) • The server does not keep track of state (except for authentication) • The client manages the logic of the application.

4. REST Examples • Assume we are making an app to track what people we meet with • We need the following resources: • Users • Meetings • We might use the following URIs • GET /user (list all users) • POST/user/1 (get information about user with ID 1) • PUT /meeting (create a new meeting) • DELETE /meeting /5 (delete meeting with ID 5) • The responses are usually JSON, e.g. { 'id': 1, 'name': 'John MacDonald', 'hometown': 'Halifax', 'occupation': 'Farmer' }

5. Using NodeJS • NodeJS is just a JavaScript interpreter. • It comes with a package manager called npm • Install packages like this: npm install <package_name> • This will install it in the current folder. • To install globally, do npm install –g <package_name> • To use Node as a webserver, you must write an application that responds to web requests. • Node has a library (HTTP) for doing this, but it’s easier to use a framework, like Express • To access a library, use the require() function

6. Using Express • Express is just a package for Node • Create a new web application with var app = express(); • Respond to requests like app.get('/user', function(req, res){ • Look at parameters through the req object • req.params for query parameters • req.body for post fields • req.files for files • Send responses through the res object • res.send("Hi mom!") • Start the application with • app.listen(<port>)

7. Client-Server Communication • On the client side, use XMLHttpRequest (or jQuery) • If you are not getting your data from the same place as your page, then you will have to use Cross Origin Resource Sharing (CORS) varxhr=newXMLHttpRequest(); //Might also use onreadystatechange xhr.onload=function() { varresponseObject = JSON.parse(this.responseText); }; xhr.open('get', 'user'); xhr.send();