Question

Let’s say you have a web page with forms, and you want to trigger a handler whenever one of those forms is submitted, or whenever a form that is added to the page at a later point in time is submitted. Which method is better:

$('form').on('submit', handler);

or

$(document).on('submit', 'form', handler);

Answer 1

If you want it to apply to forms you will add to your page later dynamically, the latter is the only version that will work at all.

(Honestly, unless your page has thousands of forms, the performance difference shouldn’t matter much anyway)