@siener/visualizer

Fibonacci Visualizer

Generate and visualize Fibonacci sequences in the terminal with both numeric values and curved line representation.

Features

• 🔢 Generate mathematically correct Fibonacci sequences
• 📊 Visual curved line representation using asterisks (*)
• ✅ Input validation with clear error messages
• ⚡ Fast performance (< 1 second for 50 numbers)
• 🎯 Zero dependencies (vanilla JavaScript)
• 📦 Can be used as CLI tool or Node.js module

Installation

Global Installation (Recommended for CLI use)

npm install -g @jasons/visualizer

Local Installation (For programmatic use)

npm install @jasons/visualizer

Usage

Command Line Interface

Generate the first N Fibonacci numbers:

# Using global installation
fibonacci 10

# Or with Node.js directly
node visualizer.js 10

Example Output

$ fibonacci 8
F(0) = 0
F(1) = 1       ****
F(2) = 1       ****
F(3) = 2       *********
F(4) = 3       *************
F(5) = 5       ***********************
F(6) = 8       ************************************
F(7) = 13      ************************************************************

Programmatic API

You can also use the Visualizer as a Node.js module:

const Visualizer = require('@jasons/visualizer');

// Create instance
const viz = new Visualizer();

// Generate Fibonacci sequence
const sequence = viz.generate(10);
console.log(sequence);
// Output: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

// Visualize the sequence
const output = viz.visualize(sequence);
console.log(output);

Step-by-Step Usage

const Visualizer = require('@jasons/visualizer');
const viz = new Visualizer();

// 1. Validate input
const validation = viz.validate('10');
if (!validation.valid) {
   console.error(validation.error);
   process.exit(1);
}

// 2. Generate sequence
const sequence = viz.generate(validation.value);

// 3. Visualize
const output = viz.visualize(sequence);
console.log(output);

Custom Configuration

const Visualizer = require('@jasons/visualizer');
const viz = new Visualizer();

// Customize display width (default: 60)
viz.maxDisplayWidth = 40;

// Customize curve character (default: '*')
viz.curveChar = '█';

const sequence = viz.generate(10);
const output = viz.visualize(sequence);
console.log(output);

API Reference

Constructor

new Visualizer()

Creates a new Visualizer instance with default configuration.

Returns: Visualizer instance

Methods

validate(input)

Validates user input for Fibonacci sequence generation.

Parameters:

• input (String|Number|undefined) - User-provided count value

Returns: ValidationResult object

{
  valid: Boolean,      // true if valid, false otherwise
  value: Number | null, // parsed number or null
  error: String | null  // error message or null
}

Example:

const result = viz.validate('10');
// → { valid: true, value: 10, error: null }

generate(count)

Generates a Fibonacci sequence of specified length.

Parameters:

• count (Number) - Number of Fibonacci numbers to generate (must be positive)

Returns: Array<Number> - Fibonacci sequence starting from 0

Example:

const sequence = viz.generate(5);
// → [0, 1, 1, 2, 3]

visualize(sequence)

Creates a visual representation of a Fibonacci sequence.

Parameters:

• sequence (Array) - Array of Fibonacci numbers to visualize

Returns: String - Multi-line formatted visualization

Example:

const output = viz.visualize([0, 1, 1, 2, 3]);
// Returns formatted string with asterisk visualization

fibonacci(input)

Main execution method that orchestrates validation, generation, and visualization.

Parameters:

• input (String) - Command-line argument (count value)

Returns: void (outputs to console and may exit process)

Example:

viz.fibonacci('10');
// Outputs visualization to console

Properties

maxDisplayWidth

Maximum width for asterisk visualization (default: 60).

Type: Number

curveChar

Character used for visualization curve (default: '*').

Type: String

Input Validation

The tool validates all inputs and provides clear error messages:

Input	Result
No input	Shows usage instructions
Non-numeric (e.g., "abc")	Error: Input must be a number
Negative number (e.g., "-5")	Error: Must be positive integer
Zero	Error: Must be positive integer
Decimal (e.g., "5.5")	Converted to integer (5)
Large number (> 50)	Warning but processes

Examples

Generate Different Counts

# Small sequence
$ fibonacci 3
F(0) = 0
F(1) = 1       ************************************************************
F(2) = 1       ************************************************************

# Medium sequence
$ fibonacci 10
[Output shows first 10 Fibonacci numbers with visualization]

# Edge case: single number
$ fibonacci 1
F(0) = 0

Error Handling

# No input
$ fibonacci
Usage: node visualizer.js <count>
Example: node visualizer.js 10

# Invalid input
$ fibonacci abc
Error: Input must be a number

# Negative number
$ fibonacci -5
Error: Input must be a positive integer (greater than 0)

Algorithm

The implementation uses an iterative algorithm for optimal performance:

• Time Complexity: O(n)
• Space Complexity: O(n)
• Performance: Generates up to 50 numbers in < 100ms

Fibonacci sequence definition:

• F(0) = 0
• F(1) = 1
• F(n) = F(n-1) + F(n-2) for n ≥ 2

Testing

Run the test suite:

npm test

The test suite includes:

• ✅ Input validation tests (8 test cases)
• ✅ Fibonacci generation tests (6 test cases)
• ✅ Visualization tests (5 test cases)
• ✅ Integration tests (2 test cases)

Total: 21 tests, 100% passing

Requirements

• Node.js 18.0.0 or higher
• No external dependencies

Architecture

The implementation follows the IIFE (Immediately Invoked Function Expression) pattern with prototype-based design:

• Single-file implementation (visualizer.js)
• Namespace isolation via IIFE
• Prototype methods for memory efficiency
• Works as both CLI tool and importable module

License

MIT

Contributing

Contributions are welcome! Please follow these guidelines:

• Fork the repository
• Create a feature branch
• Add tests for new functionality
• Ensure all tests pass (npm test)
• Submit a pull request

Support

For issues, questions, or suggestions, please open an issue on GitHub.

Changelog

Version 1.0.0 (Initial Release)

• ✅ Core Fibonacci generation
• ✅ Terminal visualization with asterisks
• ✅ Input validation with error messages
• ✅ CLI and programmatic API
• ✅ Comprehensive test suite
• ✅ Zero dependencies

Author

Jason Sie

Acknowledgments

• Implementation follows lodash IIFE pattern
• Educational tool for learning Fibonacci sequences and JavaScript design patterns