Async programming with jQuery's $.Deferred()

Background

On February 25, at the HTML5-IL meetup event, I presented a session on jQuery's $.Deferred() object, and its usage for asynchronous JavaScript programming. The slides for this session can be found here: https://docs.google.com/presentation/d/1rR7erNBn1HCBFK1lqv0W_S9zevXAAgcFBiCSM70Udsk/edit?usp=sharing

As part of this session, I included several "homework" exercises to test the attendees’ knowledge of JavaScript, and their understanding of information presented. Here are the questions:

Homework

Exercise #1

List JavaScript APIs inside the browser that are blocking, besides windows.alert(), window.confirm() and window.prompt()

Exercise #2

What is the output for:

$(document.body).append('<div>1</div>');
var d = $.Deferred();
d.done(function () {
    $(document.body).append('<div>2</div>');
});
$(document.body).append('<div>3</div>');
d.resolve();
$(document.body).append('<div>4</div>');
d.done(function () {
    $(document.body).append('<div>5</div>');
});
$(document.body).append('<div>6</div>');

Exercise #3

Describe how to use #.when() to wait on a list of deferreds, contained in a JavaScript array

Exercise #4

Create $.wait() that generates promise that resolves within specified duration

$.wait(1000).done(function () {
    alert("done");
});

Instead of

setTimeout(function () {
    alert("done");
}, 1000);

Exercise #5

Modify $.wait() to return a deferred, so that:

1. .reject() on the deferred cancels timer

2. .resolve() cancels timer, but immediately executes callbacks