title: Use string in match
body: <p>Hello i have a script where i have an textarea with the meta description and i have a input text field where i put the keyword. Then i print the matches and i have so far made this script:</p>
  
  <pre><code>var countDescription = tinymce.get('myTextEditor').getContent();
  var count =  (countDescription.match(/is/g) || []).length;
  </code></pre>
  
  <p>And it works great, but my problem is instead of matching the word "is" i want it to match my string "u"</p>
  
  <p>I have tried something like:</p>
  
  <pre><code>var count =  (countDescription.match("/" +u, "/g") || []).length;
  </code></pre>
  
  <p>But it really doesnt work..</p>
  
  <p>Hope someone can help me out.</p>