title: How can I get continuous same characters of specified length from original string by regular expression in Node.js?
body: <p>Source: <code>'aaabbbccddddhhhhlll'</code></p>
  
  <p>I want to get the <code>'aaa'</code>, <code>'bbb'</code> and <code>'lll'</code> by regular expression.</p>
  
  <p>I tried <code>/([a-z])\1{2}(?!\1)/g</code>, and I got <code>'ddd'</code> and <code>'hhh'</code> too, which I do not want.</p>
  
  <p>How should I write the regular expression?</p>
  
  <p><strong>Note</strong>: I cannot write <code>'(?&lt;!exp)'</code> or <code>'(?&lt;name&gt;exp)'</code> in Node.js while using RegExp like this:</p>
  
  <pre><code>var search_exp = new RegExp('([a-z])(?&lt;!\\1)', 'g');
  
  var search_exp1 = new RegExp('(?&lt;myname&gt;[a-z])\\k&lt;myname&gt;{2}', 'g');
  </code></pre>
  
  <p>I got <code>'Invalid group'</code> error for these.</p>
  
  <p>Did I write it wrong, or is there something special in Javascript/Node.js?</p>