This allows doing expensive computation, periodically yielding to the event loop, while keeping synchronous syntax

nonBlockingGenerator.js

function nonBlocking(generator) {
  return (...args) => {
    var callback = args[args.length - 1];
    var iter = generator(...args);
    function next() {
      try {
        var res = iter.next();
      }
      catch (e) {
        callback(e);
        return;
      }
      if (!res.done) {
        setTimeout(next, 5);
      }
      else {
        callback(null, res.return);
      }
    }
    next();
  }
}

var f = nonBlocking(function*(until) {
  var n = 0;
  for (var i=0; i<until; i++) {
    if (i % 1000 === 0) {
      console.log(i);
      yield;
    }
    n += i;  
  }
  return n;
});

f(1e5, (err, res) => {
  console.log('res: ' + res);
  clearInterval(interval);
});

var interval = setInterval(() => {
  console.log('interval');
}, 100);