I.js

I.js

function sync(gen) {
  var iterable, resume;

  resume = function(err, retVal) {
    if (err) iterable.raise(err); // raise!
    iterable.next(retVal);
  };

  iterable = gen(resume);
  iterable.next();
}

sync(function* (resume) {
  try {
    var x = firstAsync(resume);
    var y = secondAsync(resume);
    var z = thirdAsync(resume);
    // … do something with your data
  }
  catch (e) {
    console.log(e); // will catch errors from any of the three calls
  }
});

I guess there are missing yield operators on line 15, 16, 17? :-)