Introduction To Nodejs

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Recently, at work, i was tasked with providing a training session to NodeJS to help adopt node to our organization.

This post is a recap on what i covered on:

What is NodeJS?

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  • Javascript running on the server.
  • Run on Chrome V8 javascript engine.
  • Single-threaded event loop, Non-blocking I/O.
  • NPM for package management.
  • Currently version 8.4.0


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NodeJS is powered by 2 major componenent, V8 and libuv.

libuv brings asynchronous I/O to node. It should also be noted that the kestrel ( aspnet core http server ) is also leveraging libuv.

v8 is the javascript engine in node.

Why Non-Blocking I/O?

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NodeJs is designed with non-blocking evented I/O, all I/O calls are returned on callbacks. This is very different from traditional frameworks in the sense when an I/O operation is happening, no application threads is blocked.

The nature of most modern web servers are mostly I/O bound by nature. Blocking I/O is not scalable because each I/O would hold up a thread. For example, if we have 1000 I/O calls happening, then there are at least 1000 OS threads created, consuming 1000 * 10 MB of memory, context-switching in the cpu would also be really high. This is an inefficient concurrency model. Most languages/frameworks are not designed with this in mind.

  • Non-blocking I/O supports tens of thousands of concurrent connections.
  • Non-blocking IO single-threaded concurrency model.
  • Can scale to high number of concurrent requests.
  • Blocking I/O handle concurrency by having more threads.
  • More threads = more memory and cpu context-switching.
  • But Non-blocking IO without language support make code hard to read/write.

Non-Blocking I/O frameworks:

Language support for concurrency

Language support is important to prevent spaghetti code when writing concurrent code. The callback hell in nodejs early days is a good example.

With the new addition of async and await in nodejs 8, concurrency support is awesome.

IMO, Golang & C# are by far the best languages with concurrency support baked into the language.


  • Package manager for javascript.
  • Used to install node program/modules.
  • Specify dependencies in a file call package.json.
  • Modules get installed into node_modules folder.
  • NPM version 5 generate package.lock.json to guarantee similar dependencies are always restored.
  • Alternative to npm: Yarn


NodeJs is a pretty decent choice for building apps that require high I/O scalability.