title: How many possible combinations using 4 select fields
body: <p>I have four <code>HTML</code> select fields</p>
  
  <p><a href="https://i.stack.imgur.com/kH7pZ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kH7pZ.jpg" alt="enter image description here"></a></p>
  
  <p>How can I find the different number of combinations that a user can make by setting 0,1,2,3 or all 4 <code>fields</code>. I want make <code>switch cases</code> for the selected <code>parameters</code>.</p>
  
  <p><strong>EDIT :</strong></p>
  
  <p>For instance the user can select </p>
  
  <p>Category , channel , region , country</p>
  
  <pre><code>OR
  </code></pre>
  
  <p>Category , channel , region </p>
  
  <pre><code>OR
  </code></pre>
  
  <p>Category , channel </p>
  
  <pre><code>etc ...
  </code></pre>