Block execution until the callback to a function returns.

gistfile1.js

/// based off of: https://gist.github.com/1227319/957809d74d902a4d7fc44c44c946eeed38c1cd1b
/// Need to be running this code somewhere inside of a Fiber.



/// Block execution until a callback to some function is executed.
///
/// Args:
///   context:              The object context of the function (which takes a 
///                         callback) that is being called.
///   callback:             The callback argument to the current function.
///   opt_CallbackContext:  An optional object context to pass to the callback
///                         function.
Function.prototype.WaitOnCallback = function(context, callback, opt_CallbackContext) {
  var that = this;
  var caller = Fiber.current;
  var fiber = Fiber(function() {
    that.apply(context, [function(/* args */) {
      var args = Array.prototype.slice.call(arguments, 1);
      opt_CallbackContext = opt_CallbackContext || callback;
      callback.apply(opt_CallbackContext, args);
      caller.run();
    }]);
  });

  process.nextTick(fiber.run.bind(fiber));
  return Fiber.yield();
}


/// Example use:
function Database() {
  this.db_ = new Db("my_database_name",
    new Server(host, port, {auto_reconnect: true}, {}),
    {w: 1});

  this.db_.open.WaitOnCallback(this.db_, function() {
    console.log("Connected to `my_database_name` database.");
  });

}