jQuery复习 简单实现购物车功能

<table id="tb1">
            <tr>
                <td>勾选状态</td>
                <td>商品名称</td>
                <td>商品价格</td>
                <td>数量</td>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" class="a" /></td>
                <td>空调</td>
                <td class="auto-style1">2400</td>
                <td><span class="sum">+</span><input type="text" value="0" /><span class="min">-</span></td>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" class="a" /></td>
                <td>长虹电视</td>
                <td class="auto-style1">2600</td>
                <td><span class="sum">+</span><input type="text" value="0" /><span class="min">-</span></td>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" class="a" /></td>
                <td>小米3</td>
                <td class="auto-style1">2200</td>
                <td><span class="sum">+</span><input type="text" value="0" /><span class="min">-</span></td>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" class="a" /></td>
                <td>BlurAir空气净化器</td>
                <td class="auto-style1">5000</td>
                <td><span class="sum">+</span><input type="text" value="0" /><span class="min">-</span></td>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" class="a" /></td>
                <td>三星显示器</td>
                <td class="auto-style1">2000</td>
                <td><span class="sum">+</span><input type="text" value="0" /><span class="min">-</span></td>
            </tr>
        </table>
        &nbsp;<h3>总价格:<span id="spNumber"></span></h3>

<script type="text/javascript">

            $(document).ready(function () {
                $(".sum").click(function () {    添加产品数量
                    var tdlist = $(this).next("input").val();   获取文本框数量值
                    var number = parseInt(tdlist) + 1;  加一
                    var sum = 0;
                    $(this).next("input").val(number);
                    getSum();
                });
                $(".min").click(function () {   减少产品数量
                    var tdlist = $(this).prev("input").val();
                    if (tdlist > 0) {   数量不能为负
                        var number = parseInt(tdlist) - 1;  减一
                        $(this).prev("input").val(number);
                        getSum();
                    }
                });
                $(".a").click(function () {
                    getSum();
                })
                function getSum() {   获取产品总金额
                    var trlist = $("#tb1").find("tr:gt(0)");
                    var sum = 0;
                    trlist.each(function () {
                        var check = $(this).find("input[type=‘checkbox‘]").prop("checked");  勾选框为true
                        if (check == true) {
                            var monery = $(this).find(".auto-style1").text(); 获得商品单价
                            var number = $(this).find("input:text").val();    选择商品数量
                            var s = parseInt(monery) * parseInt(number);  相乘
                            sum += s;
                        }
                        $("#spNumber").text(sum);  赋值
                    });
                }
            });
    </script>