async_ticker.js

var listeners = {
  a: function(done) {
    // do something
    done();
  },
  b: function(done) {
    // do something
    done();
  }
};

function tick(done) {
  var count = 0;

  function next() {
    count -= 1;

    if (count === 0) {
      done();
    }
  }

  for (var key in listeners) {
    count += 1;
    setTimeout(listeners[key], 10, next);
  }
}

setInterval(tick, 100);