title: Increasing font size of root element in javascript based on current size (of root element)
body: <p>I am using rem units to define font sizes in my CSS and I would like to use javascript to present the end user the options to change font sizes.</p>
  
  <p>I can use pre-defined font-sizes and change the font-size using the following function:</p>
  
  <pre><code>document.documentElement.style.fontSize = "67.5%"
  </code></pre>
  
  <p>What I want to do is change the font size as a factor of the current font size. Basically something like the following:</p>
  
  <pre><code>document.documentElement.style.fontSize = Number(document.documentElement.style.fontSize) + Number(5) + "%"
  </code></pre>
  
  <p>How do I go about achieving this? </p>
  
  <p>Fiddle for playing around: <a href="http://jsfiddle.net/rahulthewall/wX94C/1/" rel="nofollow">http://jsfiddle.net/rahulthewall/wX94C/1/</a></p>