CODE EXAMPLE FOR JAVASCRIPT

credit card regex javascript

function ValidateCreditCardNumber() {

  var ccNum = document.getElementById("cardNum").value;
  var visaRegEx = /^(?:4[0-9]{12}(?:[0-9]{3})?)$/;
  var mastercardRegEx = /^(?:5[1-5][0-9]{14})$/;
  var amexpRegEx = /^(?:3[47][0-9]{13})$/;
  var discovRegEx = /^(?:6(?:011|5[0-9][0-9])[0-9]{12})$/;
  var isValid = false;

  if (visaRegEx.test(ccNum)) {
    isValid = true;
  } else if(mastercardRegEx.test(ccNum)) {
    isValid = true;
  } else if(amexpRegEx.test(ccNum)) {
    isValid = true;
  } else if(discovRegEx.test(ccNum)) {
    isValid = true;
  }

  if(isValid) {
     alert("Thank You!");
  } else {
     alert("Please provide a valid Visa number!");
  }
}