How does vue use the return value of this function?

what should I do if I want to get the return value of this method? Get the prompt undefined

in this way 
  methods: {
    test () {
      console.log(getBrowserInterfaceSize())
    },
    getBrowserInterfaceSize: function () {
      var pageWidth = window.innerWidth
      var pageHeight = window.innerHeight
      if (typeof pageWidth !== "number") {
        if (document.compatMode === "CSS1Compat") {
          pageWidth = document.documentElement.clientWidth
          pageHeight = document.documentElement.clientHeight
        } else {
          pageWidth = document.body.clientWidth
          pageHeight = window.body.clientHeight
        }
      }
      return {
        pageWidth: pageWidth,
        pageHeight: pageHeight
      }
    }
  }
Vue.js
Jun.04,2021 
methods: {
    test () {
      console.log(this.getBrowserInterfaceSize())
    },
    getBrowserInterfaceSize: function () {
        //...
    }
  }

just add a this.

but try to back up the this:

var that = this;
that. * *

Previous: About how Vue does page statistics

Next: How to introduce jq? into the project built by vue-cli

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3d16b-2bae2.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3d16b-2bae2.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?