title: Regular expression for Dutch zip / postal code
body: <p>I'm trying to build a regular expression in javascript to validate a Dutch zipcode.</p>
  
  <p>The zipcode should contain 4 numbers, then optionally a space and then 2 (case insensitive) letters</p>
  
  <p>Valid values:  </p>
  
  <pre><code>1001aa  
  1001Aa  
  1001 AA
  </code></pre>
  
  <p>I now have this, but it does not work:</p>
  
  <pre><code>var rege = /^([0-9]{4}[ ]+[a-zA-Z]{2})$/;
  </code></pre>