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 through the radio button.
But I keed having the alert for the all if statement. It looks like all the if else statements are tested.

There is the HTML code fragment: 



<code>

<p><b>Payment Information:</b></p>

         <fieldset>

            <input type=radio name=payment value=Visa id=visa />Visa &nbsp;

            <input type=radio name=payment value=Master Card />Master Card &nbsp;

            <input type=radio name=payment value=American Express />American Express &nbsp;

            <input type=radio name=payment value=Discover />Discover <br /><br />

            <label>Card Number:</label>

            <input type=text name=cardNumber id=cardNum size=30 value= onblur=ValidateCreditCardNumber() />

</code>







And there is my javascript function :



<code>



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})$/; 





    if (visaRegEx.test(ccNum) === false ){ // Visa validation

       alert(Please provide a valid Visa number!);   

        }  

      else  

        {  

         alert(Thank You!);  

        }  



    if (mastercardRegEx.test(ccNum) === false){ // MasterCard validation

        alert(Please provide a valid MasterCard number!);  

        }  

      else  

        {  

        alert(Thank You!);  

        } 



    if(amexpRegEx.test(ccNum) === false){ // Amex  validation

        alert(Not a valid America Express number!);  

        }  

      else  

        {   

        alert(Thank You!);  

        } 



    if (discovRegEx.test(ccNum) === false){ // Discover validation

        alert(Please provide a valid Discover number!); 

        }  

      else  

        {  

        alert(Thank You!);  

        } 





    }

</code>





Any kind of help or advice would be really appreciated.