A simple JavaScript program that validates credit card numbers

Regex.js

// This program uses the test() method of the regular expression object
// to check if the card number matches the pattern of the respective card type.
// The program will check for a match against a regular expression for Visa, Mastercard,
// Verve and Discover card numbers in that order. 
// If the card number is valid for a specific card type the respective 
// message will be displayed and the checking will stop.




              // pls uncomment this one by one to display

// const cardNumber = "4011211119114313";
const cardNumber = "5110762060017101";
// const cardNumber = "3471211119113123";
// const cardNumber = "6011211119113123";







const visaRegEx = /^4[0-9]{12}(?:[0-9]{3})?$/;
const mastercardRegEx = /^(?:5[1-5][0-9]{2}|222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|27[01][0-9]|2720)[0-9]{12}$/;
const verveRegEx = /^3[47][0-9]{13}/;
const discoverRegEx = /^6(?:011|5[0-9]{2})[0-9]{12}$/;


if (visaRegEx.test(cardNumber)) {
  console.log("This is a valid VISA card number.");
} else if (mastercardRegEx.test(cardNumber)) {
  console.log("This is a valid MASTERCARD number.");
} else if (verveRegEx.test(cardNumber)) {
  console.log("This is a valid VERVE card number.");
} else if (discoverRegEx.test(cardNumber)) {
  console.log("This is a valid DISCOVER card number.");
} else {
  console.log("This is not a valid card number.");
}

up we go