This is a sample to-do application for use in the PXL containers course.

The stack represents a combination of a JavaScript-based backend (Node.js with Express), a modern frontend framework (React), database technologies (SQLite and MySQL), and containerization (Docker), making it a comprehensive example for full-stack development and deployment.

The technology stack includes:

• Node.js: The backend application is built using Node.js, a JavaScript runtime environment that executes JavaScript code outside a web browser.

• Express.js: This is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It is used to create the server and handle HTTP requests.

• React.js: The frontend is built using React, a JavaScript library for building user interfaces. It is used to create the interactive UI components for the application.

• SQLite: This is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine. SQLite is used as one of the database options for the application.

• MySQL: This is a popular open-source relational database management system. In this application, MySQL is used as an alternative database option to SQLite.

• Docker: The application is designed to be containerized using Docker, which allows for isolating the application in containers to simplify deployment and scalability.

• Bootstrap & Font Awesome: For styling, the application uses Bootstrap, a front-end framework for developing responsive and mobile-first websites, and Font Awesome for icons.

• Jest: This is a JavaScript testing framework used for writing tests for the application.

• Prettier & ESLint: These are code formatting and linting tools to ensure code quality and consistency.

• package.json: Defines the Node.js application's dependencies, scripts, and other configuration details.
• src/index.js: The main entry point for the Node.js application. It sets up an Express server, initializes database connections, and defines routes for CRUD operations on 'todo' items.
• Persistence Layer (src/persistence):
  • index.js: Determines whether to use MySQL or SQLite based on the environment configuration.
  • mysql.js & sqlite.js: Implement database operations for MySQL and SQLite, respectively.
• Routes (src/routes): Contains Express route handlers for adding, deleting, retrieving, and updating 'todo' items.
• Frontend (src/static):
  • index.html: The main HTML file for the frontend.
  • app.js: A React-based frontend script that interacts with the backend to display and manage 'todo' items.

This application serves as a practical example for Docker users to understand how to containerize a simple web application using Docker.

The index.js file in the src/persistence directory currently checks for the presence of a MySQL configuration in the environment variables. If MySQL-related environment variables are set, it uses MySQL; otherwise, it defaults to SQLite. The relevant code is:

if (process.env.MYSQL_HOST) module.exports = require('./mysql');
else module.exports = require('./sqlite');

1. Environment Variables: Ensure that the environment variables for MySQL (like MYSQL_HOST, MYSQL_USER, MYSQL_PASSWORD, etc.) are correctly set in your deployment environment when you want to use MySQL. If these variables are not set, the application will default to using SQLite.

2. Database Configuration Files: The mysql.js and sqlite.js files contain the specific configurations and initialization code for each database.

By adapting these aspects of the index.js file and related configurations, you can control which database the application uses based on your deployment environment or other conditions.