How can I make a jquery-like ajax promise that has additional parameters when it succeeds?

[Peter Zingg]

Code snippet:

// passed the url from an event stream, return a promise to load the document at the url

function loadXmlDoc(url) {

  return Bacon.fromPromise($.ajax({url: url, dataType: xml}));

}

// create a stream that gets maps to a valid url when button is clicked.

var s1 = $('#load').asEventStream('click').map(getUrlToLoad);

// transform to a new stream that promises an ajax load of the document

var s2 = s1.flatMapLatest(loadXmlDoc);

  

// now do something with the document

s2.onValue(function(xml) { parseDoc(xml); } )

It's all working, but I'd like the parseDoc() function to also receive the url (location)

of the document that was loaded.  But s2 is a promise that "evaluates" to

just the xml document. I'm afraid I'm new at promises and the jquery 

ajax call. I guess there must be a way to rewrite loadXmlDoc so that the

promise that succeeds by returning an array or a dict, like:

{ data: xmlDoc, location: url  }

[mkaemmerer]

I can think of a couple ways to do this.

1) You can modify the result of the promise by using the method `then`.

function loadXmlDoc(url){
var promise = $.ajax({url: url, dataType: 'xml'})
.then(function(xml){ return {location: url, data: xml}; });
return Bacon.fromPromise(promise);
}

2) Similarly, you could modify the result of the event stream using `map`.

function loadXmlDoc(url){
var promise = $.ajax({url: url, dataType: 'xml'});
return Bacon.fromPromise(promise)
.map(function(xml){ return {location: url, data: xml}; });