title: Inline styling with DOM - backgroundColor property not being recognised
body: <p>Why does the button's background not turn blue?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>but.style.setProperty('height', '200px');
  but.style.setProperty('backgroundColor', 'blue');</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;button id="but"&gt;I am a button&lt;/button&gt;</code></pre>
  </div>
  </div>
  </p>