how to make $.when execute when one of JSON request fail

Question

I'm using the below code to get JSON from multiple urls. However, when one of the URL failed or get 404 response the function the execute doesn't work. I read the jquery doc and I know "then" should execute no matter one of the call has failed.

var data = {};
var calls = [];
for (var i in funcs) {
    calls.push(
        $.getJSON(base_url+i,
            (function(i) {
                return function(d) {
                    data[i] = d;
                };
            }(i)) 
        )
    );
}
$.when.apply($,calls).then(function() {
    do_something(data);
}); 

Answer 1

Take a look at always method. It will executed in both cases. For example:

$.when.apply($, calls).always(function() { 
    alert('Resolved or rejected'); 
});

In response to successful transaction, arguments are same as .done() (ie. a = data, b = jqXHR) and for failed transactions the arguments are same as .fail() (ie. a = jqXHR, b = errorThrown). (c)

Answer 2

I read the jquery doc and I know "then" should execute no matter one of the call has failed.

Nope, the promise only gets fulfilled if all of the passed objects are fulfilled. If one of them fails, the result will get rejected.

is there a way to make do_something(data); execute no matter if it failed or not.

You could use .always:

// doSomething waits until all are fulfilled or one is rejected
$.when.apply($,calls).always(do_something);

Yet, you probably want to execute the callback when all calls are resolved (no matter if fulfilled or rejected) - like allSettled does in Q. With jQuery, you have to work around a little:

var calls = $.map(funcs, function(_, i) {
    var d = new $.Deferred;
    $.getJSON(base_url+i).done(function(r/*…*/) {
        d.resolve(i, r);
    }, function(/*…*/) {
        d.resolve();
    });
    return d.promise();
});
$.when.apply($, calls).then(function() {
    var data = {};
    for (var i=0; i<arguments.length; i++)
        data[arguments[i][0]] = arguments[i][1];
    do_something(data);
});