I'm new to vuejs but I was trying to get the window size whenever I 
 resize it so that i can compare it to some value for a function that I 
 need to apply depending on the screen size. I also tried using the 
 watch property but not sure how to handle it so that's probably why it didn't work 

```
  methods: {

    elem() {
     this.size = window.innerWidth;
     return this.size;
   },
  mounted() {
    if (this.elem < 767){ //some code }
   }

```