jquery.whereas

"Too bad you can't use window.setTimout and have it implement the jQuery Deferred interface."

We're all upset about that. So...

"Wait. What? Now you can?!?"

Right. Now you can. I searched the internet and couldn't find an existing one, to my surprise. I wrote it for you though.

It's almost as simple as my sample code in this post explaining the basics of Deferred with the addition of an actual setTimeout... Make a $.Deferred. Call the provided func in a setTimeout, using the provided delay and parameters. After the call to the provided func, call .resolve, and in a catch block, call .reject.

"How do you use it?"

Use it just like setTimeout setTimeout:

setTimeout(function(){
    console.log("I'm in the future. " + new Date());
}, 2000);

My new $.defer method:

$.defer(function(){
    console.log("I'm in the future. " + new Date());
}, 2000);

It's the same. You can even pass parameters, just like setTimout. (I didn't bother implementing the overload that takes a string and eval's it, because who cares)

"So what's the big deal?"

• It works the same way as your beloved setTimeout, only with the $.defer, you can chain callbacks on the end...

  $.defer(function(){
      console.log("I'm in the future. " + new Date());
  }, 2000)
  .done(function(){
      console.log("All done");
  });
  

  and you get all the benefits of the rest of the callbacks - done/fail/then/always, etc.
• You can use it anywhere that expects a promise - for example, you can use it as a participant in jQuery's $.when()!
• Since there are callbacks, you have a way to get the return value of the function that you called.

  $.defer(function(){
      return "no you didn't";
  }, 2000)
  .done(function(x){
      console.log(x); // x is "no you didn't" 
  });
  

• It's cancel-able. (with optional bool parameter to reject/not reject)

  $.defer(function(){
     console.log("Doing work...");
  }, 2000)
  .progress(function(d){
      console.log("Sorry to have to cancel this.");
      d.cancel();
  })
  .done(function(){
      console.log("Won't get here.");
  })
  .fail(function(){
      console.log("This will happen");
  });

• You can use it without the function parameter to return a promise that will resolve in [delay] milliseconds

  return $.defer(100);
  

  The delay is optional too. The default delay of 0 (zero) will be used.

  return $.defer(function(){alert("ASYNC!");});
  

  or

  return $.defer();