A tiny generator helper for consuming callback code directly

run.js

function run(generator) {
  var iterator = generator(resume);
  var data = null, yielded = false;
  
  iterator.next();
  yielded = true;
  check();
  
  function check() {
    while (data && yielded) {
      var err = data[0], item = data[1];
      data = null;
      yielded = false;
      if (err) return iterator.throw(err);
      iterator.send(item);
      yielded = true;
    }
  }
  
  function resume() {
    data = arguments;
    check();
  }
}

Another example showing it can withstand sync callbacks without blowing the stack

function decr(x, callback) {
  return callback(null, x - 1);
}

run(function*(resume) {
  var x = 10000;
  while (x) {
    x = yield decr(x, resume);
  }
  console.log("Done");
});

I know this is super old but to anyone looking into generators now, iterator.send(item) should now be iterator.next(item).