title: How to make a PDF form with javascript to concatenate two fields on click OK?
body: <p><img src="https://i.stack.imgur.com/DidYS.png" alt="Please watch this image before answering "></p>
  
  <p>i want two concatenate the Username + Email Domain , On click OK button 
  and Display result in Below Full Email field. </p>
  
  <p>Javascript Code to do that please help</p>