Function _detectNearestEmptySortable

Sortable.js:961–974

(x, y)

     * @return {HTMLElement}   Element of the first found nearest Sortable
     */
    _detectNearestEmptySortable = function _detectNearestEmptySortable(x, y) {
      var ret;
      sortables.some(function (sortable) {
        var threshold = sortable[expando].options.emptyInsertThreshold;
        if (!threshold || lastChild(sortable)) return;
        var rect = getRect(sortable),
          insideHorizontally = x >= rect.left - threshold && x <= rect.right + threshold,
          insideVertically = y >= rect.top - threshold && y <= rect.bottom + threshold;
        if (insideHorizontally && insideVertically) {
          return ret = sortable;
        }
      });
      return ret;
    },
    _prepareGroup = function _prepareGroup(options) {
      function toFn(value, pull) {
        return function (to, from, dragEl, evt) {