code: function () {
        var position = this._getCaretRelativePosition();
        var offset = this.$el.offset();
  
        // Calculate the left top corner of `this.option.appendTo` element.
        var $parent = this.option.appendTo;
        if ($parent) {
           if (!($parent instanceof $)) { $parent = $($parent); }
           var parentOffset = $parent.offsetParent().offset();
           offset.top -= parentOffset.top;
           offset.left -= parentOffset.left;
        }
  
        position.top += offset.top;
        position.left += offset.left;
        return position;
      }
docs: Returns the caret's relative coordinates from body's left top corner.