Wait for the first of multiple jQuery Deferreds to be resolved?

Question

With jQuery I know that I can use $.when() to wait for all of multipe Deferreds to be resolved. (Or for the first one to be rejected.)

Answer 1

Based on Kevin B's code, here's an approach that uses a master Deferred object:

var masterDeferred = new $.Deferred(),
    reqOne = $.post("foo.php"),
    reqTwo = $.post("bar.php");

masterDeferred.done(function() {
    // do stuff
});

reqOne.done(function() {
    masterDeferred.resolve();
});
reqTwo.done(function() {
    masterDeferred.resolve();
});

I think I'm right in saying that the simplest form of resolving the masterDeferred would be :

reqOne.done(masterDeferred.resolve);
reqTwo.done(masterDeferred.resolve);

But separate done functions will allow you to branch internally and call .resolve(), .reject(), .resolveWith(...) or .rejectWith(...) as appropriate, together with masterDeferred callbacks of the general form :

masterDeferred.then( doneCallbacks, failCallbacks );