Credit Card Validator

A simple JavaScript tool to validate credit card numbers using the Luhn algorithm and detect the card type (e.g., Visa, Mastercard, American Express, Discover).

📌 Features

• Validates credit card numbers using the Luhn algorithm
• Detects card types:
  • Visa
  • Mastercard
  • American Express
  • Discover
• Auto-formats card number input with spaces (e.g., 4111 1111 1111 1111)
• Includes test cases for validation accuracy
• Works entirely in the browser – no backend required

🛠️ How It Works

1. Input Sanitization: Removes all non-digit characters from the card number.
2. Length Check: Ensures the card number is exactly 16 digits.
3. Luhn Algorithm: Validates the card number mathematically.
4. Card Type Detection: Uses regex patterns to identify the card issuer.
5. User Feedback: Displays validation result and card type on the page.

🧪 Included Tests

The script includes a small test suite that checks known valid and invalid card numbers and logs results to the browser console.

Example output in console:

Test 1: 4111 1111 1111 1111 => true (Expected: true) - PASS
Test 2: 5500 0000 0000 0004 => true (Expected: true) - PASS
...

📁 Usage

To run this project:

1. Save the code in an .html file.
2. Open it in any modern web browser.
3. Enter a credit card number and click "Validate".
4. View the result and card type on the screen.
5. Open the browser console to see test results.

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💡 Tip: Use F12 or Ctrl+Shift+I to open Developer Tools and view the console output.

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