osem-fcy/app/assets/javascripts/osem-tickets.js

function update_price($this){
    var id = $this.data('id');

    // Calculate price for row
    var value = $this.val();
    var price = $('#price_' + id).text();
    $('#total_row_' + id).text((value * price).toFixed(2));

    // Calculate total price
    var total = 0;
    $('.total_row').each(function( index ) {
        total += parseFloat($(this).text());
    });
    $('#total_price').text(total.toFixed(2));
}

$( document ).ready(function() {
    $('.quantity').each(function() {
        update_price($(this));
    });

    $('.quantity').change(function() {
        update_price($(this));
    });
    $(function () {
      $('[data-toggle="tooltip"]').tooltip()
    });
});