title: Handlebars conditional class attributes
body: <p>Using EmberJS/Handlebars, how can I add a class to an element, only if a condition is true?</p>
  
  <pre><code>&lt;div {{#if isSearching}}class="foo"{{/if}}&gt;&lt;/div&gt;
  </code></pre>
  
  <p>Like that, but less pseudocode and more reality.</p>