title: Determine which element the mouse pointer is on top of in JavaScript
body: <p>I want a function that tells me which element the mouse cursor is over.</p>
  <p>So, for example, if the user's mouse is over this textarea (with id <code>wmd-input</code>), calling <code>window.which_element_is_the_mouse_on()</code> will be functionally equivalent to <code>$(&quot;#wmd-input&quot;)</code>.</p>