Scientific Calculator

An accessible scientific calculator web app with calculation history, keyboard controls, and theme switching. The project now ships with modern tooling, automated tests, and documentation to support production-ready workflows.

Features

• Responsive and accessible calculator UI with opt-in persistent history and memory functions.
• Dark/light theme with system preference detection and user persistence.
• Input sanitisation backed by a hardened expression parser that supports parentheses, exponentiation, and unary operators.
• Automated linting (ESLint + Stylelint), formatting (Prettier), and unit tests (Vitest).

Getting Started

Prerequisites

• Node.js >= 18.18
• npm >= 9 (bundled with Node)

Installation

npm install

Available Scripts

npm run dev        # Start a static dev server at http://localhost:4173
npm test          # Run unit tests once
npm run test:watch # Run unit tests in watch mode
npm run coverage   # Run unit tests with coverage
npm run lint       # Run ESLint and Stylelint
npm run format     # Format files with Prettier

Local Development

1. Install dependencies with npm install.
2. Start the dev server: npm run dev.
3. Open http://localhost:4173 in your browser.

Project Structure

├── index.html            # Entry point with strict CSP and module loader
├── script.js             # UI logic (ES module)
├── src/
│   └── lib/
│       └── calculator.js # Pure calculation helpers & memory register
├── style.css             # Theming and layout
├── tests/                # Vitest unit tests
└── docs & tooling files  # README, SECURITY, lint configs, etc.

Environment Configuration

• Secrets or environment-specific overrides go in .env files (not committed). Provide .env.example when environment variables are introduced.
• The calculator persists theme and opt-in history preferences in localStorage; history entries expire automatically after 30 days and never leave the device.

Deployment

This is a static application. Any static host (Netlify, Vercel, GitHub Pages, S3, etc.) can serve the contents of the repository. Ensure cache headers are configured to allow quick updates (e.g., cache-busting by commit hash).

Contributing

1. Fork the repository and create a feature branch.
2. Run npm run lint and npm test before opening a pull request.
3. Follow the architecture and security guidelines in ARCHITECTURE.md and SECURITY.md.