title: How can I check a input field exists in the form when I submit it to the server?
body: <p>How can I check a input field exists in the form when I submit it to the server?</p>
  
  
  
  
  
  
  <p>For instance, I want to check whether a check box named 'mem_follow' exists or not in the form.</p>
  
  <p>Or do I have to use javascript (jquery)?</p>