title: Drop down list to create an order, cannot select the same number in each drop down list
body: <p>Good Day everyone,</p>
  
  <p>Currently working on an application, inside the settings I have a list of drop down list that my clients can select. Those drop down list are to create an order in which they want those options to appear.</p>
  
  <p>How can you make it, that they cannot select 2 times the same number, and if they do the "new" selection will go replace the "same number" with the old selection.</p>
  
  <pre><code>&lt;select name="temporary-1"&gt;
       &lt;option value="1"&gt;1&lt;/option&gt;
       &lt;option value="2"&gt;2&lt;/option&gt;
       &lt;option value="3"&gt;3&lt;/option&gt;
       &lt;option value="4"&gt;4&lt;/option&gt;
  &lt;/select&gt;
  &lt;select name="temporary-2"&gt;
       &lt;option value="1"&gt;1&lt;/option&gt;
       &lt;option value="2"&gt;2&lt;/option&gt;
       &lt;option value="3"&gt;3&lt;/option&gt;
       &lt;option value="4"&gt;4&lt;/option&gt;
  &lt;/select&gt;
  &lt;select name="temporary-3"&gt;
       &lt;option value="1"&gt;1&lt;/option&gt;
       &lt;option value="2"&gt;2&lt;/option&gt;
       &lt;option value="3"&gt;3&lt;/option&gt;
       &lt;option value="4"&gt;4&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>I am currently using jQuery in my application, so what I was thinking is to compare each Drop Down on change, and if the same number exist already I would just switch both numbers.</p>
  
  <p>Would it be a proper way? Or is there ways already to do this?</p>