jquery .find issue

I'm moving down a table using the up/down arrow keys. I am manipulating the class开发者_开发技巧 of the <tr> tags to change the CSS class (highlighted/non-highlighted). I noticed when the screen loads and I click the arrow keys the first time tr_lst.attr('id') has a value but after the 2nd click it says it is undefined.

I think it has something to do with the manipulation of the CSS in the javascript code. Any ideas on how I can get this to print out a value after every keypress?

    var tr_lst = $('#' + ListBoxVal).find('tr[class="LUGridRowHighlight"]');
    console.log('tr_lst id: ' + tr_lst.attr('id'));

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Because my comment helped you, I'm posting it as an answer:

Your selector in find could be written more simply as 'tr.LUGridRowHighlight'.

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It probably is because you do not need to use find():

var tr_lst = $('#' + ListBoxVal + " tr.LUGridRowHighlight");
console.log('tr_lst id: ' + tr_lst.attr('id'));