微信小程序调用微信支付，服务端语言nodejs

一、小程序开通微信支付、服务端域名认证步骤省略
二、创建工具函数

1、创建utils.js
2、加密算法使用插件：执行  npm install --save crypto
const wxconfig = {
    //把金额转为分
    getmoney: function (money) {
        return parseFloat(money) * 100;
    },
    // 随机字符串产生函数  
    createNonceStr: function () {
        return Math.random().toString(36).substr(2, 15);
    },
    // 时间戳产生函数  
    createTimeStamp: function () {
        return parseInt(new Date().getTime() / 1000) + '';
    },
    //签名加密算法
    paysignjsapi: function (appid,openid, body, mch_id, nonce_str, notify_url, out_trade_no, spbill_create_ip, total_fee, trade_type, mchkey) {
        var ret = {
            appid: appid,
            mch_id: mch_id,
            nonce_str: nonce_str,
            body: body,
            notify_url: notify_url,
            openid: openid,
            out_trade_no: out_trade_no,
            spbill_create_ip: spbill_create_ip,
            total_fee: total_fee,
            trade_type: trade_type
        };
        var string = this.raw(ret);
        var key = mchkey;
        string = string + '&key=' + key;
        var crypto = require('crypto');
        return crypto.createHash('md5').update(string, 'utf8').digest('hex').toUpperCase();
    },
    // 小程序签名
    paysignjsapix: function (appId, nonceStr, package, signType, timestamp, mchkey) {
        var ret = {
            appId: appId,
            nonceStr: nonceStr,
            package: package,
            signType: signType,
            timeStamp: timestamp,
        };
        var string = this.raw(ret);
        var key = mchkey;
        string = string + '&key=' + key;
        var crypto = require('crypto');
        return crypto.createHash('md5').update(string, 'utf8').digest('hex').toUpperCase();
    },
      // 对象序列化，key=value&key1=value1
    raw(args) {
        var keys = Object.keys(args);
        keys = keys.sort()
        var newArgs = {};
        keys.forEach(function (key) {
            newArgs[key] = args[key];
        });
        var string = '';
        for (var k in newArgs) {
            string += '&' + k + '=' + newArgs[k];
        }
        string = string.substr(1);
        return string;
    }
}

三、nodejs生成接口

var request = require('request');
var xmlreader = require("xmlreader");
var wxpay = require('./utils');
var appid = "xxx"// 小程序的appid
var appsecret ="xxx"// 小程序的appSecret
var mch_id = "xxx"; // 微信商户号
var mchkey = "xxx";  // 微信商户的key 32位
var notify_url = "https://www.xxx.com" //通知地址
var url = 'https://api.mch.weixin.qq.com/pay/unifiedorder';//微信支付统一调用接口
router.post("/wxpay",function(req,res){
        let out_trade_no = new Date().getTime()
        let money = req.body.money
        let openid = req.body.openid
        let nonce_str = wxpay.createNonceStr();
        let timestamp = wxpay.createTimeStamp();
        let body ='测试微信支付';
        let total_fee = wxpay.getmoney(money);
        let spbill_create_ip = req.connection.remoteAddress; // 服务ip
        let trade_type = 'JSAPI'  // 小程序： 'JSAPI'
        let sign = wxpay.paysignjsapi(appid,openid,body,mch_id,nonce_str,notify_url,out_trade_no,spbill_create_ip,total_fee,trade_type,mchkey)
        //组装xml数据
        var formData = "<xml>";
            formData += "<appid>" + appid + "</appid>"; 
            formData += "<body><![CDATA[" + "测试微信支付" + "]]></body>";
            formData += "<mch_id>" + mch_id + "</mch_id>";  
            formData += "<nonce_str>" + nonce_str + "</nonce_str>";
            formData += "<notify_url>" + notify_url + "</notify_url>";
            formData += "<openid>" + openid + "</openid>";
            formData += "<out_trade_no>" + out_trade_no + "</out_trade_no>";
            formData += "<spbill_create_ip>" + spbill_create_ip + "</spbill_create_ip>";
            formData += "<total_fee>" + total_fee + "</total_fee>";
            formData += "<trade_type>JSAPI</trade_type>";
            formData += "<sign>" + sign + "</sign>";
            formData += "</xml>";
          // 请求微信统一支付接口
        request({ url: url, method: 'POST', body: formData }, function (err, response, body) {
            if (!err && response.statusCode == 200) {
                xmlreader.read(body.toString("utf-8"), function (errors, response) {
                if (null !== errors) {
                    return;
                }
                var prepay_id = response.xml.prepay_id.text();
                let package = "prepay_id=" + prepay_id;
                let signType = "MD5";
                let minisign = wxpay.paysignjsapix(appid, nonce_str, package, signType, timestamp, mchkey);
                // 返回数据到前端
                res.send(data:{ 
                            status: '200',
                            data: { 
                                'appId': appid,
                                'mchid': mch_id,
                                'prepayId': prepay_id,
                                'nonceStr': nonce_str,
                                'timeStamp': timestamp,
                                'package':package,
                                'paySign': minisign
                            }
                      });
                });
            }
        });
})

四、小程序发起请求

pay: function () {
        let data = {
            openid: "xxxxxxxx",
            money: 0.01
        }
        wx.request({
            url: "https://xxx.com/wxpay",
            data: data,
            method: "POST",
            dataType: "json",
            success: (res) => {
                let data = res.data.data
                wx.requestPayment({
                    "timeStamp": data.timeStamp,
                    "package": "prepay_id=" + data.prepayId,
                    "nonceStr": data.nonceStr,
                    "signType": "MD5",
                    "paySign": data.paySign,
                    'success': function (res) { 
                        console.log( "支付成功", res)
                    },
                    'fail': function (res) { },
                    'complete': function (res) { }
                })
            }
        })
    },