gistfile1.txt

var q = require('q');

var a = q.defer();
var b = q.defer();

q.when(a, function() {
  console.log('calling b');
  return q.when(b, function() {
    console.log('throwing');
    throw new Error('Hello World');
  }, function (error) {
    console.log('handling error for b, rethrowing');
    throw error;
  });
}, function() {
  console.log('handling error for a');
})
.fail(function () {
  console.log('handling error for anything above');
});

b.resolve('hi');
a.resolve('yo');