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Recitation 2: Node.js


This recitation aims to highlight the basics of Node.js by walking students through the implementation of a basic To-Do app.

Staff Overview

  • Mehul Agarwal & Rohit Nanjangud Shreenivas
  • Emails: &
  • Office Hours: TBD

Full-stack Development

Different levels of the stack: - Backend - Frontend - Database - Deployment - Testing and more


What is Node?

  • Back-end JavaScript runtime environment, runs on the V8 JavaScript Engine
  • Used for server-side scripting
  • Has an event-driven architecture capable of asynchronous(non-blocking) I/O.
  • Used to build fast, powerful and scalable web applications

Asynchronous or Non-blocking I/O

Every request consists of:

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  • Non-blocking I/O allows a thread to suspend a request while it’s performing I/O to go work on a different request
  • Runs on a single-thread event loop, using non-blocking I/O calls, allowing it to support tens of thousands of concurrent connections without incurring the cost of thread context switching
  • Concurrency (in Node) refers to the Event Loop’s capacity to execute Javascript “callback” functions after completing other work

Node js async options

  • Callbacks: Functions passed to another functions
  • Promises (and promise chains): Structured callbacks
  • Generators: Functions which can be exited/paused and later re-entered
  • Async/Await: Combining generators and promises

Node Package Manager (npm)

Consists of: - npm client - command line tool - npm registry - an online database of public and paid-for private packages

The largest ecosystem of open-source libraries in the world

Model View Controller (MVC)

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Model View Viewmodel (MVVM)

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  1. mkdir into your project folder (todo-app) and cd into it
  2. npm init
  3. npm install express --save
  4. npm install body-parser --save
  5. Write express code, as seen in the reference solution
  6. node index.js (to start the server)
  7. (optional) Play with the server, send it post requests