GoldDigger - A Pure Node.js Web Application

This project was a hands-on learning experience to build a full-stack web application from the ground up, with a specific focus on creating a robust backend using only the core Node.js APIs, without any external frameworks like Express.

This document covers the backend architecture and the key concepts I learned and implemented.

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What I Learned: Core Backend Concepts

This project was my deep dive into the fundamentals of how Node.js works under the hood. By avoiding frameworks, I was forced to understand and implement the core logic that powers modern web applications.

1. Building a Node.js HTTP Server from Scratch

The entire application is built on top of the native http module.

• Key Skills:
  • Initializing a server with http.createServer().
  • Understanding the request (req) and response (res) objects.
  • Handling the asynchronous nature of the request/response cycle.
  • Making the server listen for connections on a specific port.

2. Modular Architecture with ES Modules

From the start, I structured the project into logical, reusable modules using modern ES Module syntax (import/export).

• Key Skills:
  • Setting "type": "module" in package.json.
  • Separating concerns into utils, handlers, and public directories.
  • Using import.meta.dirname to reliably create absolute paths for file system operations, which is crucial in ES Modules.

3. Implementing a Custom Router

Instead of using a pre-built router, I created my own logic to direct incoming requests based on their URL and HTTP method.

• Key Skills:
  • Inspecting req.url and req.method to differentiate between API calls and file requests.
  • Handling different HTTP verbs, specifically GET for data retrieval and POST for data submission.
  • Creating API endpoints like /api/live-price and /api/invest.
  • Sending a 405 Method Not Allowed status for incorrect HTTP methods.

4. Serving Static Files Manually

I learned how web servers serve static assets like HTML, CSS, and JavaScript by building my own static file server.

• Key Skills:
  • Using fs/promises to read file contents asynchronously.
  • Using the path module to safely join path segments and prevent security issues.
  • Creating a utility to determine the correct Content-Type header based on a file's extension (e.g., text/html vs. text/css).
  • Implementing a custom 404 "Not Found" page for requests that don't match any file.

5. Handling POST Requests and Parsing Bodies

One of the most valuable learning experiences was building a body parser from scratch to handle incoming POST data.

• Key Skills:
  • Reading an incoming request stream chunk by chunk using the for await...of loop.
  • Assembling the chunks into a complete string.
  • Parsing the string as JSON using JSON.parse().
  • Wrapping the parsing logic in a try...catch block to handle malformed JSON and prevent the server from crashing.

6. Real-Time Updates with Server-Sent Events (SSE)

To provide live gold prices, I implemented a Server-Sent Events endpoint. This was a great introduction to pushing data from the server to the client in real-time.

• Key Skills:
  • Setting the required HTTP headers for an SSE connection (Content-Type: text/event-stream, Cache-Control: no-cache, Connection: keep-alive).
  • Using setInterval on the server to periodically send data.
  • Formatting the data payload correctly with res.write('data: ...\n\n') so the client's EventSource API can parse it.

7. Business Logic and Data Persistence

I implemented the core application logic and learned to persist data on the server's file system.

• Key Skills:
  • Using the crypto module to generate a unique transaction ID with crypto.randomUUID().
  • Using fs/promises.appendFile to write transaction details to a investments.log file, ensuring a persistent record of all investments.
  • Implementing the core business logic: calculating the amount of gold purchased based on the investment amount and the current market price.

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This project solidified my understanding of the foundational layers of backend web development in the Node.js ecosystem.