Discussion with rick waldron [1] led to "Can you file a ticket: http://bugs.jquery.com so we can get a discussion going?" so here I am.

I've recently been teaching some JavaScript and some jQuery.

I've also (less) recently discovered promises and just love how they work especially when it comes to synchronizing different async events with the $.when(promise1, promise2) construct.

An exercise I gave required to fetch an RSS feed, build a DOM fragment and append it to the DOM.

In order to append something to the DOM, 2 things are required:

1) DOM is ready

2) RSS is retrieved

This is a great opportunity to use $.when with 2 promises:

$.when($.get('rss.xml'), readyP).then(function(rss){

second argument purposefully ignored since I only care about synchronization

build a document fragment

// append to the document

});

Unfortunately, there is no readyP in jQuery, so I asked the students to add the following code before the $.when:

var readyDef = new $.Deferred();

var readyP = readyDef.promise();

$(function(){ readyDef.resolve() });

This really smells like boilerplate code to me.

What about adding it to jQuery directly? Maybe defining a $.readyP?

I have no strong opinion on what the resolution value could be. Maybe the document itself?

It has to be noted that some students did the following:

$(function(){

var rssP = $.get('rss.xml')

rssP.then(function(rss){

build fragment

append to DOM

})

});

It works, but the problem is that the xhr request isn't started before the document is ready (load event in old browser) which can be late. I think that having $.readyP included in the library would be a good incitation for both good programming style and performance at the same time.

Thanks

[1] https://twitter.com/#!/rwaldron/status/179627982019764224