I mentioned some obvious benefits, like - There are 15 input-fields and all of then have an onchange event (not only, some of them have also onkeyup) So it is more pragmatic to write this kind of event-delegation ones for ALL input-fields, instead of doing it 15 times, especially if all of the HTML will be rendered with PHP's echo -> echo '... <input type=text id="someid ... />...'