Check if variable exists in a html table with javascript

$("#table").on('click','tr',function(){                   // <-- #1
   var $this    = $(this),                                // <-- #2
       filename = $this.find('td:nth-child(2)').text(),   // <-- #3
       $words   = $('#words');

   $this.addClass('selected').siblings().removeClass('selected');
   $words.html(filename).css('color','black');

   if ( valueInTable('table2', 1, filename ) ){           // <-- #4
     $words.css('color', 'blue');
   }

});

function valueInTable(tableID, columnNum, searchString){
  var found = false;
  $( '#' + tableID + ' tr td:nth-child(' + columnNum + ')' ).each(function(){
    if ($(this).text() == searchString ){
      found = true;
      return false;
    }
  });

  return found;
}

1. This is important, this binds the event to the table. When a click occurs somewhere inside the table it checks the event registry, in this case, it checks to see if a TR was clicked. This is both a performance gain, since you're not creating an event for each row of the table, but also if you create new rows dynamically, you don't have to create a new event when you do. You create this event once and it's in place for all new/old rows of the table

2. Cache $(this) into a variable. You use it more than once and chances are you'll use it even more. You should not create a new jQuery object every time you want to refer to $(this), so stick it in a variable and reuse that

3. While .html() may work for you, if you have other embedded HTML, you might get values you were not intending (e.g., <span>filename</span>), for that reason, you only need .text(), which will just give you the text value and strip off all the nested HTML (leaving you with only filename)

4. Using a function comes with a penalty, but it's good to put long-logic elsewhere, in case you're doing anything more involved. For instance, your table could expand in width (number of columns) and you might also want to search them for a value, or you might have more tables you want to look in; this same function can be used for both of those cases.

as noted, the :contains() selector was built for what you're after However, there is one caveat. The problem with contains is that it lacks customization. If you want to modify your comparison to be a RegEx, or if you want to perform other manipulation using trim or truncate, you can't do that with contains. You could easily modify the code below to do: $.trim( $(this).text() ) == $.trim( searchString )