Promises vs Events

While promises are nearly always better than Node- style callbacks, the choice of when to use promises vs a publish-subscribe approach is a bit more complex. Here are the key differences between the two approaches:

Promises Events (aka “Publish – Subscribe”)
Things that happen ONCE Things that happen MANY TIMES
Same treatment for past and future Only care about the future*
Easily matched with requests Detached from requests

Promises are often the best approach for handling responses to an explicit request, such as an HTTP call. Publish-subscribe often works better for handling actions initiated by the user (except with modals).