<script type="text/javascript">
    $(document).ready(function() {
        $('input.quantity').change(function() {
            let obAddToCartLink = document.getElementById('addtoCart');
            console.log(obAddToCartLink);
            let link_str = String(obAddToCartLink);
            replace_str = link_str.replace(/(quantity=)[0-9]+/ig, '$1'+$(this).val());
            obAddToCartLink.setAttribute('href', replace_str);
        });
        $('input.quantity').keypress(function() {
            $(this).trigger('change');
        });
        $('a.price-card__quantyty-plus, a.price-card__quantyty-minus').click(function(e){
            e.preventDefault();
            e.stopPropagation();
            var oThisQuntityInput = $('input.quantity:first', $(this).parent().parent());
            var iThisQuantity = parseInt(oThisQuntityInput.val());
            var iSubtrahend = 1;
            if ($(this).hasClass("price-card__quantyty-plus"))
            {
                if (iThisQuantity < 2)
                {
                    return false;
                }
                iSubtrahend = iSubtrahend * (-1);
            }
            var iThisQuantityNew = iThisQuantity + iSubtrahend;
            oThisQuntityInput.val(iThisQuantityNew);
            oThisQuntityInput.trigger('change');
        });
    });
</script>

<a class="price-card__quantyty-plus" href="#">+</a>
<input type="text" class="quantity price-card__quantyty-count" name="QUANTITY_1" value="1" id="QUANTITY_1">
<a class="price-card__quantyty-minus" href="#">-</a>
<a href="<?= $arResult["ADD_URL"] . '&quantity=1' ?>" id="addtoCart" class="addtoCart btn-basket">В корзину</a>