// 在支付成功的回调中调用 getPaidUnionId 接口
   wx.requestPayment({
     timeStamp: '...',  // 时间戳
     nonceStr: '...',    // 随机字符串
     package: 'prepay_id=xxxxxx',  // 预支付id
     signType: 'MD5',
     paySign: 'xxxxxx',  // 签名
     success(res) {
       if (res.errMsg === 'requestPayment:ok') {
         // 支付成功，调用 getPaidUnionId 接口获取 UnionId
         wx.getPaidUnionId({
           // ...其他参数
           success: function(paidUnionIdRes) {
             const paidUnionId = paidUnionIdRes.paidUnionId;
             console.log('支付宝 UnionId:', paidUnionId);
           },
           fail: function(error) {
             console.error('获取支付宝 UnionId 失败:', error);
           }
         });
       }
     },
     fail(res) {
       console.log('支付失败:', res);
     }
   });