title: drag and drop in vue js without component
body: <p>I want to use html 5 drag and drop in vue js .</p>
  
  <p>I see the w3schools tutorial about drag and drop . 
  It works in a simple html file but doesn't work in my vue project</p>
  
  <p>My tutorials code and link is :
  w3schools - drag  : <a href="https://www.w3schools.com/jsref/event_ondrag.asp" rel="noreferrer">https://www.w3schools.com/jsref/event_ondrag.asp</a>
  and my error says :
  Uncaught ReferenceError: allowDrop is not defined</p>
  
  <p>I define all methods in method scope in vue js.</p>