/**
   * Propagates the observable sequence or Promise that reacts first.
   *
   * @example
   * var = Rx.Observable.amb(xs, ys, zs);
   * @returns {Observable} An observable sequence that surfaces any of the given sequences, whichever reacted first.
   */
  Observable.amb = function () {
    var acc = observableNever(),
      items = argsOrArray(arguments, 0);
    function func(previous, current) {
      return previous.amb(current);
    }
    for (var i = 0, len = items.length; i < len; i++) {
      acc = func(acc, items[i]);
    }
    return acc;
  };