$(document).ready(function() {
  var highlighted = "";
  var column = 3;

  var positionTooltip = function(event) {
    var tPosX = event.pageX;
    var tPosY = event.pageY + 20;
    $('div.tooltip').css({top: tPosY, left: tPosX});
  };
  var showTooltip = function(event) {
    $('div.tooltip').remove();
    var $thisAuthor = $(this).text();
    if ($(this).parent().is('.highlight')) {
      highlighted = 'un-';
    } else {
      highlighted = '';
    };
    $('<div class="tooltip">Click to ' + highlighted +
                    'highlight all articles written by ' +
                            $thisAuthor + '</div>').appendTo('body');
    positionTooltip(event);
  };
  var hideTooltip = function() {
    $('div.tooltip').remove();
  };

  $('table.striped td:nth-child(' + column + ')' ...