201912G13/Shop/web/js/main.js

$(function () {
    var CartPlusMinus = $('.cart-plus-minus');
    CartPlusMinus.prepend('<div class="dec qtybutton">-</div>');
    CartPlusMinus.append('<div class="inc qtybutton">+</div>');
    $(".qtybutton").on("click", function() {
        var $button = $(this);
        var oldValue = $button.parent().find("input").val();
        if ($button.text() === "+") {
            var newVal = parseFloat(oldValue) + 1;
        } else {
            // Don't allow decrementing below zero
            if (oldValue > 0) {
                var newVal = parseFloat(oldValue) - 1;
            } else {
                newVal = 1;
            }
        }
        $button.parent().find("input").val(newVal);
    });
})