title: Add attributes without values using d3.js
body: <p>How could I add attributes without values using d3.js?</p>
  
  <p>For example, how could I construct such an option:</p>
  
  <pre><code>&lt;option value="" disabled selected&gt;Select something...&lt;/option&gt;
  </code></pre>
  
  <p>In this example the <code>disabled</code> and <code>selected</code> attributes have no value. And <code>value</code> attribute has a value of <code>""</code>.</p>