代码前提：只需要替换两个与自己相关的参数key和mch_id

1、小程序开通微信支付成功，去公众平台(https://mp.weixin.qq.com/)；

成功后可以知道自己的mch_id，即商户号。

2、去这里：商户平台(https://pay.weixin.qq.com/)，获取key = API密钥

小程序端：

wx.cloud.callFunction({   name: 'wepay',   success: res => {     console.log(res.result)     if (!res.result.appId) return     wx.requestPayment({       ...res.result,       success: res => {         console.log(res)       }     })   } })

云函数wepay：

const key = "ABC...XYZ"//换成你的商户key，32位 const mch_id = "1413092000"//换成你的商户号 //以下全部照抄即可 const cloud = require('wx-server-sdk') const rp = require('request-promise') const crypto = require('crypto') cloud.init() function getSign(args) {   let sa = []   for (let k in args) sa.push(k + '=' + args[k])   sa.push('key=' + key)   return crypto.createHash('md5').update(sa.join('&'), 'utf8').digest('hex').toUpperCase() } function getXml(args) {   let sa = []   for (let k in args) sa.push('<' + k + '>' + args[k] + '</' + k + '>')   sa.push('<sign>' + getSign(args) + '</sign>')   return '<xml>' + sa.join('') + '</xml>' } exports.main = async (event, context) => {   const wxContext = cloud.getWXContext()   let appId = appid = wxContext.APPID   let openid = wxContext.OPENID   let attach = 'attach'   let body = 'body'   let total_fee = 1   let notify_url = "https://mysite.com/notify"   let spbill_create_ip = "118.89.40.200"   let nonceStr = nonce_str = Math.random().toString(36).substr(2, 15)   let timeStamp = parseInt(Date.now() / 1000) + ''   let out_trade_no = "otn" + nonce_str + timeStamp   let trade_type = "JSAPI"   let xmlArgs = { appid, attach, body, mch_id, nonce_str, notify_url, openid, out_trade_no, spbill_create_ip, total_fee, trade_type }   let xml = (await rp({ url: "https://api.mch.weixin.qq.com/pay/unifiedorder", method: 'POST', body: getXml(xmlArgs) })).toString("utf-8")   if (xml.indexOf('prepay_id') < 0) return xml   let prepay_id = xml.split("<prepay_id><![CDATA[")[1].split("]]></prepay_id>")[0]   let payArgs = { appId, nonceStr, package: ('prepay_id=' + prepay_id), signType: 'MD5', timeStamp }   return { ...payArgs, paySign: getSign(payArgs) } }

packge.json:

{   "name": "wepay",   "version": "1.0.0",   "description": "",   "main": "index.js",   "scripts": {     "test": "echo \"Error: no test specified\" && exit 1"   },   "author": "",   "license": "ISC",   "dependencies": {     "wx-server-sdk": "latest",     "crypto": "^1.0.1",     "request-promise": "^4.2.2"   } }