title: submit button on html to output result on same page
body: <p>Although this seems like something very basic, but no matter what I tried I couldn't get my head around it. Basically I want a html form where a user types in their ID number in an input text box and when they hit the submit button it displays their email address which is their company ID number @ company.com, such as below</p>
  
  <pre><code>&lt;form action=""&gt; ID Number: &lt;input
  type="text" name="idnumber" /&gt;&lt;br/&gt;
  &lt;input type="submit" value="Whats my
  email address" /&gt; &lt;/form&gt; &lt;p&gt;Your
  email address is
  'idnumber'@email.com&lt;/p&gt;
  </code></pre>
  
  <p>Can this even be done using html or would I need to use  Javascript or PHP for it?</p>
  
  <p>Thanks</p>