jDeferred.js

$.ajax({
    success: function (data) {
        console.log("Yay! You gots datums!");
    },
    error: function (jqXHR, status, error) {
        console.log("Error? Handled it.");
    },
    complete: function () {
        console.log("It's over.");
    }
});


$.ajax().done(function (data) {
    console.log("Yay! You gots datums!");
}).fail(function (jqXHR, status, error) {
    console.log("Error? Handled it.");
}).always(function () {
    console.log("It's over.");
});

doAThing().then(function () {
    console.log(
        "Do another thing" +
        "after the previous thing is done"
    );
});

var doAThing = function () {
    var deferred = jQuery.Deferred();
    deferred.fail(function () {
        throw("Aw, snap.");
    });
    return deferred;
};

var doAThing = function () {
    return jQuery.Deferred().fail(function () {
        throw("Aw, snap.");
    });
};