title: How can I use window size in Vue? (How do I detect the soft keyboard?)
body: <p>In my mobile web app with Vue, I want to hide my footer when the soft keyboard pops. So I have a little function to test the ratio of window height to window width...</p>
  
  <pre><code>showFooter(){
      return h / w &gt; 1.2 || h &gt; 560;
  }
  </code></pre>
  
  <p>...and I declare window.innerHeight/window.innerWidth in my data.</p>
  
  <pre><code>    data: { h: window.innerHeight, w: window.innerWidth }
  </code></pre>
  
  <p>Trouble is, when window.innerHeight changes, my h property doesn't get the new value. How can I watch window.innerHeight ?</p>