title: Retrieve element size in mm (or in non px unit)?
body: <p>I'm studying browser DOM with Javascript and building a "system" that relies on millimeter units instead of px.
  I know how to set element sizes in mm, that works well with</p>
  
  <pre><code>element.style.width = "32mm"; for example.
  </code></pre>
  
  <p><strong>However I am having trouble retrieving the measurements in any other units than in px. Is there a way to do thi</strong>s?</p>
  
  <p>SIDENOTE: Is there no way to define a global default unit system for css? Would be handy to define what units to use once, and then just use plain values for elements.</p>