docs: function appendScript( script ) {
          currentlyAddingScript = script;
  
          // If BASE tag is in play, using appendChild is a problem for IE6.
          // See: http://dev.jquery.com/ticket/2709
          baseElement
              ? headElement.insertBefore( script, baseElement )
              : headElement.appendChild( script );
  
          currentlyAddingScript = null;
      }