title: Calculating how long a form has been filled out in JavaScript
body: <p>So I have a form on my webpage and I want to implement a system which tells the user how long he filled out the form.</p>
  
  <p>Is it possible to start a counter variable (timer) on JavaScript when the user starts filling out any textfield on the form, then send this counter data after he presses the submit button? I'd like to send this as a POST argument to another page, which would tell the user how long he filled out the previous page's form.</p>