What comes first .always() or .then() callbacks in jQuery?

Question

If you have a function which has both .then and .always callbacks, which one will get executed first?

And I just did, took one minute, and I was right -> **http://jsfiddle.net/adeneo/ou1sy6uw/** — adeneo, Apr 23 '15 at 00:31
However, swapping them, they return differently -> **http://jsfiddle.net/adeneo/ou1sy6uw/1/**, so whatever order they are added — adeneo, Apr 23 '15 at 00:33
The best would be to not rely on the order. Single threaded JS by default is protected from concurrency issues, if only we don't do silly things in our code. — zerkms, Apr 23 '15 at 01:16

score 9 · Accepted Answer · edited Aug 07 '17 at 11:16

Taken from the deferred.resolve() documentation:

When the Deferred is resolved, any doneCallbacks added by deferred.then() or deferred.done() are called. Callbacks are executed in the order they were added.

Example below:

var $logger = $("#logEntry");
function addLog(content){
   $logger.append($("<li/>").html(content));
}

var newPromise = $.Deferred();

$.when(newPromise).done(function() {
    addLog("1st $when().done!");
});

newPromise.then(function() {
    addLog("1st then!");
}).always(function() {
    addLog("1st always!");
}).done(function() {
    addLog("1st done!");
}).done(function() {
    addLog("2nd done!");
}).always(function() {
    addLog("2nd always!");
}).then(function() {
    addLog("2nd then!");
});

$.when(newPromise).done(function() {
    addLog("2nd $when().done!");
});

addLog("Resolving promise!");

newPromise.resolve();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<ul id="logEntry"></ul>

In your example `always` is attached to `then`, which is a bit different from what OP asked. — zerkms, Apr 23 '15 at 01:19

What comes first .always() or .then() callbacks in jQuery?

1 Answers1