微信小程序借助云开发云函数实现支付功能 省去后台搭建

前提：
1.你的小程序不是个人小程序
2.有微信商户号和商户密钥

小程序端 购买按钮方法

buyBtnAction:function(){
    wx.cloud.callFunction({
      name:'xiadanpay',
      data:'',
      success:function(e){
        //云函数返回的需要的支付参数
        wx.requestPayment({
          timeStamp: e.result.timeStamp,
          nonceStr: e.result.nonceStr,
          package: e.result.package,
          signType: e.result.signType,
          paySign: e.result.paySigns,
          success:function(res){
            console.log('支付成功！！！！！！')
          },
          fail:function(e){
            console.log('支付失败')
          }
        })
      },
      fail:function(err){
        console.log(err)
      }
    })
  },

云函数端

const cloud = require('wx-server-sdk')
const ip = require('ip')


// 初始化 cloud
cloud.init()
const appId = 'xxxxx' // 小程序appid
const mchId = 'xxxxxx' //商户id
const key = 'xxxxxxx'//商户密匙
const timeout = 10000 // 毫秒
const {
  WXPay,
  WXPayConstants,
  WXPayUtil
} = require('wx-js-utils');
let wxpay = new WXPay({
  appId,
  mchId,
  key,
  timeout,
  signType: WXPayConstants.SIGN_TYPE_MD5,
  useSandbox: false   
});
exports.main = async (event, context) => {
  const wxcontext = cloud.getWXContext();
  var time_stamp_jj = '' + Math.ceil(Date.now() / 1000)
  // 统一下单
  var reqObj = {
    body: '商城-商品1',
    out_trade_no: '1478582754971',   //订单号每次支付不能重复,(这里写死仅做测试)
    total_fee: 1,   //支付费用   （单位是分不是元）   
    spbill_create_ip: ip.address() || '127.0.0.1',
    notify_url: 'http://www.qq.com',
    trade_type: 'JSAPI',
    time_stamp: time_stamp_jj,
    openid: wxcontext.OPENID
};
  var resobj = await wxpay.unifiedOrder(reqObj)
  var preid = 'prepay_id=' + resobj.prepay_id
  const paySign = await WXPayUtil.generateSignature({
    appId: resobj.appid,
    nonceStr: resobj.nonce_str,
    package: preid,
    signType: 'MD5',
    timeStamp: time_stamp_jj
  }, key);
//返回给小程序端调起支付的支付参数
  return{
    timeStamp:time_stamp_jj,
    nonceStr: resobj.nonce_str,
    package:preid,
    signType:'MD5',
    paySigns:paySign
  }
}