<script type="text/javascript">var calculateTotalPrice = function() {
    var checkboxes = document.querySelectorAll('input[type=checkbox]');
    var totalPrice = 0;

    for(var i = 0; i < checkboxes.length; i += 1) {
        if (checkboxes[i].checked) {
             totalPrice = totalPrice + parseInt(checkboxes[i].value, 10);
        }
    }

    console.log(totalPrice);

    document.querySelector('.total-price').innerHTML = totalPrice;
};

window.onload = function() {
    var checkboxes = document.querySelectorAll('input[type=checkbox]');

    for(var i = 0; i < checkboxes.length; i += 1) {
        checkboxes[i].addEventListener('click', calculateTotalPrice, false);
    }
};
</script>