Code to validate Payment methods

Wizpert3.html

<form id="optionForm">
  <select name="submitted[Which_your_registration][select]" id="edit-submitted-which-your-registration-select" class="select-or-other-select form-select required">
    <option selected="selected" value="">- Select -</option>
    <option value="credit_card">Pay by credit card</option>
    <option value="send_me_an_invoice">Send me an invoice</option>
    <option value="select_or_other">Contact me by phone</option>
  </select>
  <label for="payment">Payment Method:</label>
  <input type="radio" name="payment" id="paypal" value="paypal" /> PayPal
  <input type="radio" name="payment" id="google" value="google" /> Google Wallet
  <input type="radio" name="payment" id="credit" value="credit" /> Credit Card
  <br />
  <input type="submit" id="edit-submit" value=" Pay Now! " />
</form>
<script language="javascript">
  var $ = function (id) {
    return document.getElementById(id);
  }
  $("edit-submit").onclick = checkPayment;
  function checkPayment() {
    var choices = $("edit-submitted-which-your-registration-select");
    var userChoice = choices.options[choices.selectedIndex].value;
    if (userChoice == "") {
      window.alert("You must select a choice!");
      return false;
    } else if (userChoice == "credit_card") {
      window.open("https://www.paypal.com/");
    }
    
    if ($("paypal").checked) {
      window.open("https://www.paypal.com/");
    } else if ($("google").checked) {
      window.open("http://www.google.com/wallet/");
    } else if ($("credit").checked) {
      window.open("https://www.authorize.net");
    }
  }
</script>