demo.html

<div class="main">
    <div class="hr">演示代码</div>

    <p><input  id="money" name=money placeholder="输入金额,单位:分"></p>

    <p>
        <input  type="radio" name="pay"  value="wxpay" checked > 微信支付
        <input  type="radio" name="pay"  value="alipay" > 支付宝
        <input  type="radio" name="pay"  value="jdpay" > 京东钱包
        <input  type="radio" name="pay"  value="qpay" > QQ钱包
    </p>

    <!-- 支付代码接入 开始 -->
    <script
                src="https://payjs.cn/pay.js"
                mch="12r1f1"
                id="popfeng"
                amount="10">
            </script>
    <!-- 支付代码接入 结束 -->

</div>

<script src="//cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<script>
    $(function(){
        $(":radio").click(function(){
            var value = $(this).val();
            $("#popfeng").attr("pay",value);
        });
        $("#money").bind("input propertychange", function() {
            var value = $(this).val();
            $("#popfeng").attr("amount",value);
        });
    });
</script>