How To Create a JSON Database In NodeJs From Scratch

Photo by Tim Evans on Unsplash

In order to teach myself my ways of working with NodeJs, Javascript, and Typescript, I have built many versions of a file-based JSON database over the years, especially when I did not want to settle on a database setup for my project.

For this tutorial, I’ll show you how to put a file-based JSON database together quickly and enjoy every related algorithm. We will look into:

• Using file system module to read-write files;
• Create a powerful query API for the data;
• Handle data CRUD actions;
• Analyse ways to improve the data read-write performance;

Start a Typescript Node Project

I wrote a post on how to set up a Typescript Node project and shared it as a template you can clone and start a Node project. That’s the environment I will be using for this tutorial so simply run the following command to create your project:

git clone git@github.com:beforesemicolon/node-typescript-project-template.git

Make any necessary changes to the project and, let’s get going!

Implementation

I always start anything by walking backward from the developer experience. Then, I write the code for the behind-the-scenes to support those interactions. I call it DX-driven development.

I picture the database being started like so:

interface ToDo {
  id: string,
  name: string;
  status: "pending" | "completed" | "archived";
  user: {
    name: string;
  };
}

const db = new JSONDB<ToDo>("todo");

It should simply take the name of the JSON file where all the data will be placed and take a generic type which should work like a schema of the data to help with the developer experience. The code behind this should look like so:

// src/db/JSONDB.ts

import path from "path";
import fs from "fs";

class JSONDB<T extends object> {
  private readonly filePath: string;

  constructor(private fileName: string) {
    this.filePath = path.join(__dirname, `${fileName}.json`);

    if (!fs.existsSync(this.filePath)) {
      fs.writeFileSync(this.filePath, "[]", "utf-8");
    }
  }
}