It is a basic API built using VANILLA NodeJS and I am emphasizing on the word 'vanilla' so much because there are tons of videos and blogposts on the internet on 'create a REST API using Node' but most using Express. I wanted to learn how things in Express work under the hood. This one has no database, I have used file system to read from and write into JSON data.
This is always a nice thing to know why do we want to learn some new technology or framework or library. For example lets take Express. You cannot know the importance of learning it unless you have faced the challenges of creating an API without using it. You have to manually handle everything and there is no luxury of using built-in middlewares. Have a look at this one to get a better closure on how Express do certain things under the hood. Obviously I have not implemented everything that Express provides but yes, you can get a basic understanding.
You just have to have Node installed in your machine to spin up the server. Use node server.js or if you have nodemon installed globally then nodemon server.js while in the current directory to get the server up and running on PORT = 5000. Happy Coding!
An useful Link on how to handle incoming data from client