title: javascript regex matching 3 digits and 3 letters
body: <p>How to match word in string that contain exactly "3 digits and 3 letters"?    </p>
  
  <p>e.g. 100BLA</p>
  
  <pre><code>var regex = ?;
  var string = "word word 100BLA word";
  desiredString = string .match(regex);
  </code></pre>