getElementById in Polymer element
<p>How can I use getElementById in a Polymer custom element?</p>

<p>Here is my element:</p>

<pre><code>&lt;link rel="import" href="../bower_components/polymer/polymer.html"&gt;
&lt;link rel="import" href="../styles/shared-styles.html"&gt;

&lt;dom-module id="bb-calendar"&gt;

  &lt;template&gt;

    &lt;style is="custom-style" include="shared-styles"&gt;&lt;/style&gt;

    &lt;div class="card"&gt;
            &lt;paper-toolbar&gt;
                &lt;div title&gt;Calendar&lt;/div&gt;
            &lt;/paper-toolbar&gt;
            &lt;div id="hideme"&gt;
                &lt;div&gt;this should be hidden&lt;/div&gt;
            &lt;/div&gt;
    &lt;/div&gt;

  &lt;/template&gt;

  &lt;script&gt;

    Polymer({

      is: 'bb-calendar',

      ready: function() {
        document.getElementById("hideme").style.display = 'none';
      }

    });

  &lt;/script&gt;

&lt;/dom-module&gt;
</code></pre>

<p>When I run the code I get this error message: <code>Uncaught TypeError: Cannot read property 'style' of null</code></p>

<p>Obviously I'm doing something wrong but I don't know what.</p>