credit card input validation using regular expression in javascript

Question

I\'ve been trying to get this done but no success. I am using regular expression to validate the credit card number entered by user based on the type of credit card selected thr

Answer 1

You have 4 different if blocks in your case, which hits every single block when the previous once fail.

Replace if with if else, that way if will only validate for a single use case. Also you need not let the user know to be specific about the type of card that he is trying to enter. Just a single message to enter a valid number should suffice.

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!");
  }
}