[Igorsrt]

попробовал исправить свой код
html в браузере выглядит:

<p class="quantity_wanted_p" style="display: inline;">
<input type="text" name="ajax_qty_to_add_to_cart[78]" id="quantity_wanted_78" class="text" value="1" size="2" maxlength="3">									

 <a href="#" data-field-qty="ajax_qty_to_add_to_cart[78]" class="btn btn-default button-minus product_quantity_down">
                                                <span>
                                                    <i class="fa fa-minus"></i>
                                                </span>
                                            </a>
<a href="#" data-field-qty="ajax_qty_to_add_to_cart[78]" class="btn btn-default button-plus product_quantity_up">
                                                <span>
                                                    <i class="fa fa-plus"></i>
                                                 </span>
                                            </a>				
 </p>

js:

// The button to increment the product value
$(document).on('click', '.product_quantity_up', function(e){
    e.preventDefault();
    fieldName = $(this).data('field-qty');
    var currentVal = parseInt($('input[name='+fieldName+']').val());
	if (!allowBuyWhenOutOfStock && quantityAvailable > 0)
		quantityAvailableT = quantityAvailable;
	else
		quantityAvailableT = 100000000;
    if (!isNaN(currentVal) && currentVal < quantityAvailableT)
        $('input[name='+fieldName+']').val(currentVal + 1).trigger('keyup');
    else
        $('input[name='+fieldName+']').val(quantityAvailableT);
});
 // The button to decrement the product value
$(document).on('click', '.product_quantity_down', function(e){
    e.preventDefault();
    fieldName = $(this).data('field-qty');
    var currentVal = parseInt($('input[name='+fieldName+']').val());
    if (!isNaN(currentVal) && currentVal > 1)
        $('input[name='+fieldName+']').val(currentVal - 1).trigger('keyup');
    else
        $('input[name='+fieldName+']').val(1);
});

Что не так?