text: //app.js
  App({
    onLaunch: function () {
      //调用API从本地缓存中获取数据
      var logs = wx.getStorageSync('logs') || []
      wx.setStorageSync('logs', logs)
    },
    getUserInfo: function(cb){
      var that = this
      if(this.globalData.userInfo){
        typeof cb == "function" && cb(this.globalData.userInfo)
      }else{
        //调用登录接口
        wx.login({
          success: function () {
            wx.getUserInfo({
              success: function (res) {
                that.globalData.userInfo = res.userInfo
                typeof cb == "function" && cb(that.globalData.userInfo)
              }
            })
          }
        })
      }
    },
    getSystemInfo: function (cb) {
      var that = this
      if(that.globalData.systemInfo){
        typeof cb == "function" && cb(that.globalData.systemInfo)
      }else{
        wx.getSystemInfo({
          success: function(res) {
            that.globalData.systemInfo = res
            typeof cb == "function" && cb(that.globalData.systemInfo)
          }
        })
      }
    },
    globalData:{
      userInfo: null,
      systemInfo: null
    }
  })
  