title: IN Operator in Javascript functions like the one in SQL
body: <p>I have tried the following but it's throwing an exception:</p>
  
  <pre><code>                if (!$get('sslot_hf0').value in ('X', 'Y', 'Z', '0')) {
                  $get('sslot_hf0').value = 'X';
              }
  </code></pre>
  
  <p>I am looking for a function similar to the <code>IN</code> operator in <code>SQL</code></p>