multi shipping in tinystoragecart checkout

checkout.html

<select id="shippingselect">
  <option disabled selected value>Select</option>
  <option value="2" data-shippingselect="15">Europe Shipping +15€</option>
  <option value="3" data-shippingselect="35">International Shiping +35€</option>
</select>

main.js

var $cartcheckoutshippingselection = document.getElementById('shippingselect');
if ($cartcheckoutshippingselection) {
	$cartcheckoutshippingselection.addEventListener('change', function(e) {
		$singleShipping.dataset.shippingcost = e.target.selectedOptions[0].dataset.shippingselect;
		requirejs(['cart/cart'], function(cart) {
			document.dispatchEvent(
				new CustomEvent('calculateCartSum', {
					detail: {
						cart: cart.getStorageCart(),
						cartTotal: cart.calculateTotal(),
						cartObject: cart
					}
				})
			);
		});
	});
}