simple jQuery Deferred example

jquery.deferred.promise.js

function getData() {
    var deferred = $.Deferred();

    $.ajax({
        'url': 'http://google.com',
        'success': function(data) {
            deferred.resolve('yay');
        },
        'error': function(error) {
            deferred.reject('boo');
        }
    });

    return deferred.promise();
}

$.when(getData()).done(function(value) {
    alert(value);
});

getData().then(function(value) {
	alert(value);
});

thanks, just one note: for testing purposes it would be better to use 'url': window.location.origin or one may come across cross-origin request issue

$.ajax already returns a deferred/promise.

function getData() {
    return $.ajax({
        'url': 'http://foo.com',
        'success': function(data) {
            return data;
        },
        'error': function(error){
            console.log("An error occurred:", error);
        }
    });
}

$.when(getData).then(function(value) {
    if(value){
        alert(value);
    } else {
         console.log("Successful ajax call, but no data was returned");
    }
});

@jeremyroelfs thank you for the clarification, this was me attempting to learn and document some commonly used patterns but obviously my understanding at the time wasn't correct

I think its awesome you doing gists of your work! Keep it up man! That helps others!!!

Complete example!

function getData() {
    var deferred = $.Deferred();

    $.ajax({
        'url': 'http://google.com',
        'success': function(data) {
            deferred.resolve('yay');
        },
        'error': function(error) {
            deferred.reject('boo');
        }
    });

    return deferred.promise();
}

$.when(getData()).done(function(value) {
    alert(value);
});

getData().then(
function(value) {
	alert(value);
},
function (error) {
    alert(error);
});