Simple flow control for multiple parallel async calls.

var done = waitress(count, cb);

Waitress returns a function, done, that will wait to be called count times before executing the cb passed into it.

var done = waitress(3, function(err) {
  if (err) throw err;
done(new Error('oh noes')); // causes callback to be fired with an error condition 
done(false); // also causes callback to be fired with an error condition 

If done receives a second parameter, waitress will add that to an array, which will be the second parameter given to the callback, as long as it receives no errors.

The array will be built in the order the data is received, not the order done appears in your code.

var done = waitress(3, function(errresult) {
  if (err) throw err;
  result === ['a', 'b', 'c'];
done(null, 'a');
done(null, 'b');
done(null, 'c');