🧮 FizzBuzz Application (TypeScript)

A clean, testable implementation of the classic FizzBuzz problem — built in TypeScript using a modular architecture.

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Overview

This application takes a range of numbers (min to max) and applies FizzBuzz rules:

• Numbers divisible by 3 → "Fizz"
• Numbers divisible by 5 → "Buzz"
• Numbers divisible by both 3 and 5 → "FizzBuzz"
• Other numbers → the number itself

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🚀 Features

• Extensible: Easy to add new rules by implementing the FizzBuzzStrategy interface
• Priority System: Rules are sorted by priority to ensure correct evaluation order
• Input Validation: Validates user input for numbers and ranges
• Type-Safe: Full TypeScript implementation with proper typing
• Testable: Clean code makes unit testing straightforward
• Error Handling: Comprehensive error handling with user-friendly messages

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🧠 How It Works

1. The InputHandler asks the user for a minimum and maximum number.
2. The FizzBuzzApplication validates the input and generates results.
3. The FizzBuzzFormatter applies a set of rules:
   • FizzRule: multiples of 3 → "Fizz"
   • BuzzRule: multiples of 5 → "Buzz"
   • FizzBuzzRule: multiples of both 3 and 5 → "FizzBuzz"
4. The formatted result is printed in the console.

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⚙️ Installation

Clone the repository and install dependencies:

git clone https://github.com/k-angama/fizzbuzz-ts.git
cd fizzbuzz-ts
npm install

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▶️ Run the Application

Build and execute the CLI app:

npm start

You’ll be prompted to enter a minimum and maximum number.

Example:

Enter minimum number: 1
Enter maximum number: 15

=== ✅ FizzBuzz Result ===

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz

=== ✅ End ===

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🧪 Running Tests

This project uses Jest for unit and integration testing.

Run the test suite:

npm test

Typical test coverage includes:

• FizzBuzzStrategy rules
• FizzBuzzFormatter logic
• FizzBuzzApplication flow and error handling

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🧩 Project Structure Details

Project Structure

src/
├── core/
│   ├── application/
│   │   ├── FizzBuzzApplication.ts
│   │   └── InputHandler.ts
│   ├── rules/
│   │   ├── FizzBuzzFormatter.ts
│   │   └── FizzBuzzStrategy.ts
│   └── fizzbuzz.ts
├── main.ts
__tests__/
└── (unit tests)

Core Components

FizzBuzzStrategy: Interface defining the contract for all rules

• priority: Determines evaluation order (higher = first)
• rule(): Boolean condition for when the rule applies
• value: String to return when the rule matches

FizzBuzzFormatter: Manages and applies rules

• Sorts rules by priority
• Finds the first matching rule for each number
• Returns formatted output string

FizzBuzzApplication: Application controller

• Handles user input flow
• Validates input
• Returns structured result object

InputHandler: Abstracts user input

• Interface allows for easy mocking in tests
• Implementation uses readline

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🧑‍💻 Author

k.angama
GitHub • LinkedIn

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🪪 License

This project is released under the MIT License.