If you are very much concerned about performance of your website or webpage, you must surely get into practice of finding out useless elements used. This would not give a very high performance but a good practice and can be assured of minute lag issue.
console.log('This page has ' + $('*').length + ' elements!');
In the above snippet * indicates all elements of the page. This universal selector is passed to jQuery and the count is logged. You can play with the output by using alert() or store into variables.