Does Events Handlers in JavaScript for one event fired as FIFO, LIFO or in parallel?

Question

Does Events Handlers in JavaScript for one event fired as FIFO, LIFO or in parallel?

Answer 1

PPK has an excellent writeup on Event bubbling and Event Capturing.

http://www.quirksmode.org/js/events_order.html

Answer 2

It's very simple. DOM Level 2 Events module does not specify order in which event listeners are to be fired. However, DOM Level 3 Events module does specify order to be the same as registration one.

First registered — first fired.

Note that DOM Level 3 Events module is still a draft, whereas Level 2 one is a recommendation. Nevertheless, modern browsers often follow semantics of exactly this draft Level 3 specification, instead of an older Level 2 one.

In practice, IIRC, only IE doesn't respect order of event listeners. All other browsers implement it as FIFO (and as described in DOM L3 Events). You can also find related tests online :)