promise-example.js

// using a promise

$.when(doStuff('eat'), doStuff('sleep')).then(function(a, b){
  console.log(a + ' and ' + b +' are done');
});

// define the function that returns a promise
function doStuff (subject) {
  var defer = new $.Deferred();
  
  console.log('starting '+ subject +'...');
  
  // do some async action
  setTimeout(function () {
    if (subject) defer.resolve(subject);
    else defer.reject();
  }, 1000);
  
  // return the promise immediately
  return defer.promise();
}