title: Alternative for Math.log2
body: <p>So I have this script that use Javascript's <code>Math.log2()</code> function. Tested it in IE 9 today and found out that IE does not support log2. It only supports log. </p>
  
  <p>Does anyone know of a way that I can get the same result as log base 2? An example of my code is below:</p>
  
  <pre><code>var number = 16,
      exponent = Math.log2(number);
  
  //Will return 4
  return exponent;
  </code></pre>