[wp-trac] [WordPress Trac] #21170: JavaScript actions and filters

[WordPress Trac]

#21170: JavaScript actions and filters
----------------------------+-------------------------
 Reporter:  koopersmith     |      Owner:  koopersmith
     Type:  task (blessed)  |     Status:  new
 Priority:  normal          |  Milestone:  3.5
Component:  General         |    Version:  3.4
 Severity:  normal          |   Keywords:
----------------------------+-------------------------
 The concept of adding JavaScript actions and filters has been tossed
 around for some time. We've experimented with various configurations of
 actions in both the fullscreen and customizer APIs, and they've proven
 their utility enough to graduate them to a core feature in their own
 right.

 ----

 I think that a good events API should satisfy these parameters:

 1. '''Support jQuery-style dot namespacing''' to allow functions to be
 easily removed.

 2. '''Should (likely) support priorities.''' While seemingly random
 numbers aren't fun to use, it allows plugins to cooperate without having
 to know of each other's existence. We can't expect plugin authors to
 rearrange the array of callbacks.

 3. '''Should ''not'' force functions to have unique IDs.''' Anonymous
 functions are extremely common in JavaScript — forcing them to be named is
 contrary to the nature of the language.

 4. '''Should be structured as a mixin.''' The global event loop should be
 an instance of the core Events object. Using a mixin will allow developers
 to easily create event loops for their own plugins (to prevent  polluting
 the global namespace — think about large plugins, like bbPress). An events
 mixin will also enable developers to create more powerful abstractions,
 such as observable values, collections, and pretty much any structural JS
 object you can dream up.

 5. '''Should allow the looping process to be overwritten.''' This will
 result in less code and added flexibility. The only difference between
 actions and filters is how they handle the callbacks object. There are
 other types of looping processes that could be beneficial in JS. One
 example would be returning false if any callback returns false, which
 could be used to stop a process, much like the native
 event.stopPropagation method.

 ----

 '''Why not use custom jQuery events?'''

 Custom jQuery events are great when we need to trigger actions on a DOM
 element. Triggering plain events on the body element (or any other hidden
 element) is not performant — every jQuery event normalizes an DOM Event
 object, which we then completely ignore.

 '''Should we require jQuery to use the API?'''

 I'm not sure. jQuery.Callbacks may be a helpful solution here, provided we
 can properly integrate priorities and namespacing. jQuery.Callbacks also
 only requires jQuery.each and jQuery.extend, so writing a shim that
 doesn't use the rest of jQuery would not be exceptionally difficult.
 Either way, switching between one and the other as we develop should not
 be exceptionally difficult.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/21170>
WordPress Trac <http://core.trac.wordpress.org/>
WordPress blogging software