code: function distance(direction, currentRect, targetRect) {
                  if (direction === 'left' && targetRect.left < currentRect.left) {
                      return currentRect.left - targetRect.left;
                  }
                  if (direction === 'up' && targetRect.top < currentRect.top) {
                      return currentRect.top - targetRect.top;
                  }
                  if (direction === 'right' && targetRect.left > currentRect.left) {
                      return targetRect.left - currentRect.left;
                  }
                  if (direction === 'down' && targetRect.top > currentRect.top) {
                      return targetRect.top - currentRect.top;
                  }
                  return 0;
              }
docs: Calculates the distance to the ClientRect in a given direction.
  Allows for keyboard navigation based on the relative visual location of the element.
  
  @param {string} direction 'up', 'left', 'right' or 'down',
  @param {ClientRect} currentRect The position of the current item.
  @return {Number}