title: Add HTML Attribute without a value using Jquery
body: <p>I want to add an attribute to a HTML element without a value using JQuery</p>
  
  <pre><code>&lt;input id="r1" type="radio name="r1" value="1"&gt;
  </code></pre>
  
  <p>Add <code>required</code></p>
  
  <pre><code>&lt;input id="r1" type="radio name="r1" value="1" required&gt;
  </code></pre>
  
  <p>How can this be done without the <code>=""</code>after the attribute?</p>