I plan to use data attributes to identify elements in the DOM for test cases of selenium. Will using attributes affect application performance?
Not at all, you'll be fine using attributes data-*. However, it should be noted that using syntax is $.data(theInput, 'someData');much faster than using syntax theInput.data('someData');, as shown in this jsPerf .
data-*
$.data(theInput, 'someData');
theInput.data('someData');