Изменение количества товаров в InstantShop

 
<input name="qty" style="width:30px;text-align:center" value="1" id="num_count" />
<input type="button" value="-" id="button_minus">
<input type="button" value="+" id="button_plus">
 
<script>
var numCount = document.getElementById('num_count');
var plusBtn = document.getElementById('button_plus');
var minusBtn = document.getElementById('button_minus');
plusBtn.onclick = function() {
var qty = parseInt(numCount.value);
qty = qty + 1;
numCount.value = qty;
}
minusBtn.onclick = function() {
var qty = parseInt(numCount.value);
qty = qty - 1;
numCount.value = qty;
}
</script>
 

<script type="text/javascript" >
        {literal}
                         $(document).ready(function() {
                         $('.minus_qty').click(function () {
                          var $input = $(this).parent().find('input');
                          var count = parseInt($input.val()) - 1;
                          count = count < 1 ? 1 : count;
                          $input.val(count);
                          $input.change();
                          return false;
                         });
                        $('.plus_qty').click(function () {
                        var $input = $(this).parent().find('input');
                        $input.val(parseInt($input.val()) + 1);
                        $input.change();
                        return false;
                        });
                        });
        {/literal}
</script>
 

<span class="minus_qty">-</span><input name="qty" style="width:40px !important;text-align:center; border: none;" class="amount" value="1" /><span class="plus_qty">+</span>