Add Credit Card Validator with documentation (#1455)

Author: Ratheshan03

Regular Expressions/Credit Card Number Validator/README.md

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+# Credit Card Validator Regular Expression
+
+This JavaScript module provides a regular expression for validating credit card numbers from major card providers such as Visa, MasterCard, American Express, Discover, Diners Club, and JCB. It ensures that the card number follows the correct structure and length for each provider.
+
+## Features:
+
+- Supports major credit card providers: Visa, MasterCard, American Express, Discover, Diners Club, and JCB.
+- Validates the structure, length, and format of the card numbers.
+- Simple and efficient to use for front-end or back-end applications.
+
+## Usage:
+
+```javascript
+const creditCardRegex = /^(?:4[0-9]{12}(?:[0-9]{3})?|        // Visa
+                          5[1-5][0-9]{14}|                   // MasterCard
+                          3[47][0-9]{13}|                    // American Express
+                          6(?:011|5[0-9]{2})[0-9]{12}|       // Discover
+                          3(?:0[0-5]|[68][0-9])[0-9]{11}|    // Diners Club
+                          (?:2131|1800|35\d{3})\d{11})$/;    // JCB
+
+function validateCreditCard(cardNumber) {
+  return creditCardRegex.test(cardNumber);
+}
+
+// Example usage:
+console.log(validateCreditCard('4111111111111111')); // Visa, true
+console.log(validateCreditCard('5555555555554444')); // MasterCard, true
+console.log(validateCreditCard('378282246310005'));  // American Express, true
+console.log(validateCreditCard('6011111111111117')); // Discover, true
+console.log(validateCreditCard('30569309025904'));   // Diners Club, true
+console.log(validateCreditCard('3530111333300000')); // JCB, true
+console.log(validateCreditCard('1234567812345670')); // Invalid, false
+```

Regular Expressions/Credit Card Number Validator/validateCreditCard.js

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+// Credit Card Number Validator
+// This regex validates credit card formats from Visa, MasterCard, American Express, Discover, Diners Club, JCB, and more.
+
+const creditCardRegex =
+  /^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|3[47][0-9]{13}|6(?:011|5[0-9]{2})[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$/;
+
+function validateCreditCard(cardNumber) {
+  return creditCardRegex.test(cardNumber);
+}
+
+// Example usage:
+console.log(validateCreditCard("4111111111111111")); // Visa, true
+console.log(validateCreditCard("5555555555554444")); // MasterCard, true
+console.log(validateCreditCard("378282246310005")); // American Express, true
+console.log(validateCreditCard("6011111111111117")); // Discover, true
+console.log(validateCreditCard("30569309025904")); // Diners Club, true
+console.log(validateCreditCard("3530111333300000")); // JCB, true
+console.log(validateCreditCard("1234567812345670")); // Invalid, false