Dev Journal

A simple Node.js project to log your daily learning entries. This project demonstrates core Node.js concepts such as environment variables, file system operations, routing, and serving static files.

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Table of Contents

• Project Overview
• Getting Started
• Environment Variables
• Why Use the path Module?
• Handling Directory Paths in Node.js
• CORS and OPTIONS Preflight Requests
• Routing and URL Parsing
• API vs Static File Routing
• Project Structure

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Project Overview

Dev Journal is a Node.js application that allows you to record and view daily learning entries. It uses a simple JSON file as a database and serves both API endpoints and static HTML/CSS files.

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Getting Started

1. Clone the repository
2. Install dependencies (if any)
3. Set up your .env file (see below)
4. Run the server:

   node index.js

5. Visit http://localhost:9000 (or your configured port)

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Environment Variables

Why use process.env.PORT || 3000?

This pattern sets the port number for your server:

const PORT = process.env.PORT || 3000;

• process.env.PORT: Uses the port defined in your environment (e.g., by cloud providers like Heroku, AWS, Azure).
• 3000: Fallback default if no environment variable is set.

Why is this important?

• Cloud providers dynamically assign ports at runtime.
• Hardcoding a port (like 3000) can cause your app to crash on deployment.
• Using .env files lets you easily switch between development, testing, and production environments without changing your source code.

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Why Use the path Module?

File paths differ across operating systems:

• Windows: data\entries.json
• Mac/Linux: data/entries.json

Hardcoding / or \ can break your code on another OS. The Node.js path module ensures your file paths are always correct, regardless of the platform.

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Handling Directory Paths in Node.js

Modern Node.js (v20.11.0+)

const __dirname = import.meta.dirname;
const __filename = import.meta.filename;

Older Node.js Versions

import { fileURLToPath } from "url";
import path from "path";

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

This ensures compatibility and correct path resolution in all environments.

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CORS and OPTIONS Preflight Requests

When making POST, PUT, or DELETE requests from a browser, an OPTIONS preflight request is sent first. If your server doesn't handle this, requests from real frontends will fail.

Example handling:

if (req.method === "OPTIONS") {
  res.writeHead(204, {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "GET, POST, OPTIONS",
    "Access-Control-Allow-Headers": "Content-Type",
  });
  res.end();
  return;
}

This enables cross-origin requests and ensures smooth API communication.

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Routing and URL Parsing

To determine which route a user is visiting, Node.js uses the URL object:

const requestUrl = new URL(req.url, `http://${req.headers.host}`);
const pathname = requestUrl.pathname;

• req.url: The requested path (e.g., /about?name=favour)
• req.headers.host: The domain and port (e.g., localhost:3000)
• pathname: Extracts just the path, without query parameters.

Full URL	Pathname
http://localhost:3000/	/
http://localhost:3000/about	/about
http://localhost:3000/user?id=5	/user

This makes route handling clean and robust.

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API vs Static File Routing

In routes.js:

• API routes (e.g., /api/entries) must be handled before static file routes.
• Static files (HTML, CSS) are served for paths like /, /entries.html, /style.css.
• Unmatched routes return a 404 JSON error.

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Project Structure

.env
.gitignore
index.js
package.json
Readme.md
routes.js
controllers/
  entryController.js
data/
  entries.json
public/
  entries.html
  index.html
  style.css
utils/
  helper.js

• controllers/: API logic (reading/writing entries)
• data/: JSON "database"
• public/: Static HTML/CSS files
• utils/: Helper functions (responses, static file serving)

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Learn More

• Node.js Documentation
• dotenv
• MDN: CORS
• Node.js Path Module

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Happy journaling!