title: Draw a connecting line between two elements
body: <p>How can I draw a line between two or more elements to connect them? Any combination of HTML/CSS/JavaScript/SVG/Canvas is fine.</p>
  <p>If your answer supports any of these, then do mention it:</p>
  <ul>
  <li>draggable elements</li>
  <li>draggable/editable connections</li>
  <li>element overlap avoidance</li>
  </ul>
  <blockquote>
  <p>This question has been updated to <a href="https://stackoverflow.com/questions/linked/6278152">consolidate the numerous variations</a> of it.</p>
  </blockquote>