var requestlib = require("request");
  var urllib = require("url");
  var crypto = require('crypto');
  var url = "https://api.mch.weixin.qq.com/pay/unifiedorder";
  var urlObj = urllib.parse(url);
  var option = {
    "url": urlObj,

    "method": "POST"
  };
  option.headers = {
    "Content-Type": "application/x-www-form-urlencoded"
  };
  //1. 参数部分
  var dataobj = {
    "appid": "【微信开放平台审核通过的应用APPID】",
    "mch_id": "【微信支付分配的商户号】",
    "nonce_str": "【随机字符串】",
    "body": "商品描述",
    "out_trade_no": "【订单号 32字符以内 平台自己的订单号】",
    "total_fee": 1,//金额 原金额*100 以分为单位
    "spbill_create_ip": "【后台服务器IP地址】",
    "notify_url": "【回调接口地址】",
    "trade_type": "APP"
  };
  //2.字典排序用于签名，并同步拼接xml参数
  var keys = Object.keys(dataobj)
    .sort();
  var params = [];
  var final = "<xml>";
  for (let i = 0; i < keys.length; i++) {
      var v = keys[i];
      params.push(v + "=" + dataobj[v]);
    final += "<" + v + ">" + dataobj[v] + "</" + v + ">";
    }
  //3.此处注意需要加上支付密钥
  params.push("key=【这里是支付密钥】");
  var str = params.join("&");
  //4.开始MD5签名，注意转大写字母
  var sign = crypto.createHash("md5")
    .update(str)
    .digest('hex')
    .toUpperCase();
  //5.完成最后的拼接xml参数，并发起请求
  final += "<sign>" + sign + "</sign></xml>";
  option.body = final;
  return when.promise(function(resolve, reject, notify) {
    requestlib(option, function(e, r, b) {
      if (e) {
        reject(e);
      }
      resolve(b);
    });
  });

2. 自行解析返回xml

console.log(JSON.stringify(retX));//返回的结果，次数仅处理正确结果
  var dataobj = {};
  //去掉干扰手动解析项
  retX = retX.replace(/<\!\[CDATA\[/g,"").replace(/\]\]>/g,"").replace(/<\!\[CDATA\]>/g,"null");
  //提取所需参数的key
  var keys = ["appid","nonce_str","mch_id","prepay_id","trade_type"];
  for (let i = 0; i < keys.length; i++) {
      var v = keys[i];
  //拼接正则取值
    var re= new RegExp("<"+v+">(.*)</"+v+">");
    dataobj[v]=re.exec(retX)[1];
//     console.log(re.exec(retX)[1]);
  }
  //最终的dataobj为返回数据解析结果

 var crypto = require('crypto');
//   console.log(JSON.stringify(obj));
  var dataobj2 = {
    "appid": dataobj.appid,
    "partnerid": dataobj.mch_id,
    "prepayid": dataobj.prepay_id,
    "package": "Sign=WXPay",
    "noncestr": dataobj.nonce_str, //这里偷懒，直接使用返回值的随机字符串
    "timestamp": moment()
      .format("X") //使用moment获取时间秒数 注意是秒数
  };
  //字典排序
  var keys = Object.keys(dataobj2)
    .sort();
  var params = [];
  for (let i = 0; i < keys.length; i++) {
      var v = keys[i];
      params.push(v + "=" + dataobj2[v]);
    }
  params.push("key=【支付密钥】");
  var str = params.join("&");
  var sign = crypto.createHash("md5")
    .update(str)
    .digest('hex')
    .toUpperCase();
  dataobj2.sign = sign;
//dataobj2 为最终的参数集，可用手机调用支付