title: How to copy input of one field to another?
body: <p>This is my html code. How do I directly generate a roll number from registration number and branch?
  For example, if reg no = 20140087 and branch = BT then in the roll number section , the reg. no and branch would automatically come as 14/BT/_. I only need to provide number in _. 14 would come from 2014 of reg no.</p>
  
  <pre><code>&lt;br&gt;&lt;br&gt;&lt;label&gt;Registration Number: &lt;/label&gt;
              &lt;input id="reg" class="text-input" type="text" name="registrationnumber" placeholder="20140087" required&gt;
              &lt;br&gt;&lt;br&gt;&lt;label&gt;Branch: &lt;/label&gt;
              &lt;select style="float:right;"&gt;
                &lt;option value="bt"&gt;BT&lt;/option&gt;
                &lt;option value="ch"&gt;CH&lt;/option&gt;
                &lt;option value="ce"&gt;CE&lt;/option&gt;
                &lt;option value="cse"&gt;CSE&lt;/option&gt;
                &lt;option value="ece"&gt;ECE&lt;/option&gt;
                &lt;option value="ee"&gt;EE&lt;/option&gt;
                &lt;option value="it"&gt;IT&lt;/option&gt;
                &lt;option value="me"&gt;ME&lt;/option&gt;
                &lt;option value="mme"&gt;MME&lt;/option&gt;
              &lt;/select&gt;
  
              &lt;br&gt;&lt;br&gt;&lt;label&gt;Roll No: &lt;/label&gt;
              &lt;input id="roll" class="text-input" type="text" name="roll" placeholder="14/IT/11" required&gt;
  </code></pre>