How to know the browser width and height on each browser ?

How to know the browser width and height on each browser ?

Hi, for now, I'm doing this with this code :

   
    
    
  1.  var navWidth, navHeight;
    if (self.innerWidth != undefined)
    {
     navWidth = self.innerWidth;
     navHeight = self.innerHeight;
    } else {
     navWidth = document.documentElement.clientWidth;
     navHeight = document.documentElement.clientHeight;
    }
    2.
The problem is that it's not working on Android browser :/

How can I fix that please ?