uniapp获取手机硬件设备信息，后台取不到

data() {
return {
platform: '',
mobileModel: '',
deviceId: '',
system: '',
windowWidth: ''

        }  

},
onLoad() {
uni.getSystemInfo({
success: function(res) {
// console.log(res.platform);
// console.log(res.model);
// console.log(res.system)
// console.log(res.windowWidth)
// console.log(res.deviceId)
var platform = res.platform
this.platform = platform //ios

                var mobileModel = res.model  
                this.mobileModel = mobileModel //iphone  

                var system = res.system  
                this.system = system  

                var deviceId = res.deviceId  
                this.deviceId = deviceId  

                var windowWidth = res.windowWidth  
                this.windowWidth = windowWidth  

            }  
        });  
    },  

发送给后台
this.$request.post('/register', {
deviceId: this.deviceId,
platform: this.platform,
mobileModel: this.mobileModel,
system: this.system,
windowWidth: this.windowWidth
}).then((regres) => {}
后台为空，前台可以打印，哪里写错了吗