如何选择多个单选按钮并计算总价？

<form id="orderForm">
  <input type="radio" name="size" value="small"> Small
  <input type="radio" name="size" value="medium"> Medium
  <input type="radio" name="size" value="large"> Large
  
  <input type="checkbox" name="toppings" value="cheese"> Cheese
  <input type="checkbox" name="toppings" value="pepperoni"> Pepperoni
  <input type="checkbox" name="toppings" value="mushrooms"> Mushrooms
  
  <button type="button" onclick="calculateTotal()">Calculate Total</button>
</form>

Total Price: <span id="totalPrice"></span>

function calculateTotal() {
  var size = document.querySelector('input[name="size"]:checked').value;
  var toppings = document.querySelectorAll('input[name="toppings"]:checked');
  
  var sizePrice = 0;
  switch (size) {
    case 'small':
      sizePrice = 5;
      break;
    case 'medium':
      sizePrice = 10;
      break;
    case 'large':
      sizePrice = 15;
      break;
  }
  
  var toppingsPrice = 0;
  for (var i = 0; i < toppings.length; i++) {
    toppingsPrice += 2;
  }
  
  var totalPrice = sizePrice + toppingsPrice;
  document.getElementById('totalPrice').textContent = totalPrice;
}