Abstracting async ops with promises

fbapp.js

// So let's say you have an async operation that doesn't 
// use a jQuery-ajax method. In my example, I'll use a call 
// to the FB API, which just takes a callback function 
// which gets called with a ```resp``` object.

  FB.api('/platform', function(resp) {
    if (resp.data) {
      success();
    } else if (resp.error) {
      error();
    }
  });

// We can do better.

  function getPage(page) {
    var dfd = $.Deferred();
    FB.api(page, handleResp(dfd));
    return dfd.promise();
  }
  
  function handleResp(dfd) {
    return function(resp) {
      if (resp.data) {
        dfd.resolve(resp.data);
      } else if (resp.error) {
        dfd.reject(resp.error);
      } else {
        dfd.reject("Something went wrong!");
      }
    }
  }

// Now we can use API methods just like Ajax calls!

  getPage('/platform')
    .done(function(data) {
      doStuff();
    })
    .fail(function(error) {
      handleError();
    });
    
// And handle multiple async requests, and be 
// notified when they're all done

  $.when(getPage('/platform'), getPage('/otherPage'))
    .done(function(platform, otherPage) {
      // do stuff
    });