const updateManager = wx.getUpdateManager()
    
    updateManager.onCheckForUpdate(function(res) {
      // 请求完新版本信息的回调 
      console.log(res.hasUpdate ? '有新版本' : '无新版本')
    })


    updateManager.onUpdateReady(function() {
      wx.showModal({
        title: '更新提示',
        content: '新版本已经准备好，是否重启应用？',
        success: function(res) { 
          if (res.confirm) {
            // 新的版本已经下载好，调用 applyUpdate 应用新版本并重启
            updateManager.applyUpdate()
          }
        }
      })
    })
在app.js onLaunch中执行以上代码，上报了以下错误
小程序后台错误日志：
Cannot read property \'onCheckForUpdate\' of undefined

TypeError: Cannot read property \'onCheckForUpdate\' of undefined

at je.onLaunch (https://app.js:18:19)

at je.<anonymous> (https://lib/WASubContext.js:2:2201446)

at new je (https://lib/WASubContext.js:2:2202688)

at a.<anonymous> (https://lib/WASubContext.js:2:2202819)

at https://lib/WASubContext.js:2:2180329

at https://app.js:4:1

at u (https://lib/WASubContext.js:2:2244637)

at https://usr/app-service.js:6194:10