What is Node.js? An explanation too late
You may wonder “Dude! What the hell? Node.js has been around for 7 years and now you are writing a blog on What is Node.js”. I do agree with you but too often I have a conversation like this in my office
Tom: Hey Rahul, I need your help. I wanna take over the world.
Me: Sure Tom. I can do that in Node.js. I think I recently saw a node module for that.
Tom: Cool! I will setup the application server for you to deploy this.
Me: I wouldn’t need that. Node.js, dude!
Tom: Oh! So Node.js is an application server? I thought Node.js is a programming language.
Me: No No! Javascript is the language we code. Since its script based I don’t need a containerized application server.
Tom: Is it? So is Node.js is a JS library?
Me: Not exactlyyyy…
Tom: Then it must be that JS Framework from Facebook everyone talks about these days.
Me: Tom, thats React.js and I wouldn’t categorize Node.js as a framework.
Tom: What else do I have, huh, Is it a webserver like Apache Tomcat?
Me: No, but Node.js has inbuild modules that helps me to create to a webserver.
Tom: So what the **** is Node.js?
Me: Basically, Node.js is a ……
I work in an ecosystem of autobots and decepticons(i.e) one team living in the open source world while the other teams endorse typical enterprise tool based development culture. As we converge too often these days, I thought of writing this to take a deep dive into what exactly is Node.js
V8 Javascript Engine — Under the Hood
Let me teach you some basics of computers. Our computers consists of processors, which when given a command, executes it. But in order to talk to a processor, we need a language
Tom: Oh! Ok I get it now. So Node.js is that language which talks to the processors
No. It isn’t. Processors do not understand high level languages rather you have to provide them with Instruction Sets(Machine Code). But writing machine code isn’t easy. Lets just take a peek
Understood anything? Me neither. There are different types of instruction sets for different types of processors. So the code we write must be converted into these instruction sets for the processor to execute. This conversion must be performed by some process and this is where Javascript engines make their entrance.
A Javascript engine is a program that converts Javascript code into instruction sets that the machine can understand. There are many JS engines created and maintained by technology leaders of the world and the most popular among them is the V8 Javascript Engine developed by Google. World’s famous browser, Google Chrome, runs on top of V8 Javascript engine.
ECMAScript
Tom: How does V8 or any other Javascript engine know how to convert javascript to machine code? Are there any standards defining what any piece of javascript code must contain?
Yes, there is. Everybody puts your hands together for ECMAScript. ECMAScript defines the language specification for javascript describing each and every components of javascript, their functionalities, etc. All the javascript engines use ECMAScript specifications to convert javascript code to Machine code.
C++
Tom: Rahul, Weren’t we talking about Javascript? Why are we jumping to C++ now?
Tom, V8 engine is written in C++ and before you question me why is that important, take a look at the screenshot of V8 homepage shown below
As highlighted, V8 can run standalone or can be embedded into any C++ application. So if I write a C++ program, I can embed V8 and process any js code that I write.
V8 also has hooks that I can use in my C++ program to add addition features to Javascript and can expose multiple features for people to code to. Since I am writing C++ code, I can add hell a lot of feature. Javascript was supposed to be browser based language and now with the plethora of library that exists with C++, I can add a lot of new functionality(access file system, db connection, etc) to Javascript.
This is exactly what Node.js does. But in a very larger scale adding features to Javascript which were never expected to be a part of Javascript community.
Tom: Does that mean Node.js is also written in C++
Spot on Tom!!! Node.js is written in C++ and it embeds V8 to convert js to machine code and introduces innumerable features into the Javascript ecosystem.
Henceforth, if asked what is Node.js, reply
Node.js is a program that converts javascript to machine code by embedding V8 engine in its C++ code and provides humongous capabilities to Javascript and monstrous power to Javascript developers”
