node实现生成带参数的小程序二维码并保存到本地

var requestp = require('request-promise');
var fs = require('fs'); // 载入fs模块

var wxapi = {};
module.exports = wxapi;
//获取二维码
wxapi.qrcode = async (ctx, next) => {
  //获取aess_token
  var aess_token = global.aess_token
  var qrcodeurl = 'https://api.weixin.qq./wxa/getwxacode?aess_token='+aess_token
  let options = {
    method: 'POST',
    uri: qrcodeurl,
    encoding:null,
    body: {
      "path": 'pages/index/index?openid='+ctx.query.openid,//带参数的path
      "width":280,
      "is_hyaline":false
    },
    json: true
  }
  var imgname='./public/images/'+ ctx.query.openid+'.jpg'
  var imgnameback=ctx.query.openid+'.jpg'
  fs.exists(imgname, function (exists) {
    //判断图片是否存在
    if(!exists){
      //通过微信接口获取小程序码
      requestp(options)
      .then(function (body) { 
        var base64Img = body.toString('base64'); // base64图片编码字符串
        var dataBuffer = new Buffer(base64Img, 'base64');
        //保存到本地
        fs.writeFile(imgname, dataBuffer, function(err) {
          if(err){
            console.log(err);
          }else{
            console.log("保存成功！");
          }
        });
      })
      .catch(function (err) {
        console.log(err)
      });
    }
  })
  //返回图片名
  ctx.body = {
    code: 1,
    img: imgnameback
  }
};