小程序 globalData undefined 如何解决

function request(requestMapping, data, requestWay, contentType) {
  wx.showLoading({
    title: '请稍后',
  })
  return new Promise(function(resolve, reject) {
    console.log('请求中。。。。。')
    wx.request({
      url: '自己的服务器地址' + requestMapping,
      data: data,
      header: {
        'content-type': contentType // 默认值
      },
      timeout: 3000,
      method: requestWay,
      success(res) {
        //console.log(res)
        if (res.data.success == false || res.data.statusCode == 404) {
          reject(res)
        } else {
          resolve(res)
        }
      },
      fail: (e) => {  
        wx.showToast({
          title: '连接失败',
          icon: 'none'
        })},
      complete: () => {
        wx.hideLoading()
      }
    })
  })
}

//获取 openid
function getOpenId(app, that){
  return new Promise(function (resolve, reject) {
        wx.login({
          success: function (yes) {
            // 发送 res.code 到后台换取 openId, sessionKey, unionId
            var requestMapping = '/testopenid'
            var data = {
              code: yes.code
            }
            var requestWay = 'GET'
            var contentType = 'application/json'
            var p =request(requestMapping, data, requestWay, contentType)
            p.then(res => {
              //console.log(res) 做一些后续操作
              app.globalData.openId = res.data;
                    resolve(res)
            }).catch(e => {
              reject(e)  
            })
          },
          fail(e) {
            console.log(e)
          }
        })  
  })
}

getOpenId(getApp(),this);