code: function joint(streams) {
    if (!(streams instanceof Array)) {
      streams = Array.prototype.slice.call(arguments);
    }
  
    return streams.reduce(function(thru, stream) {
      if (stream) {
        thru.pipe(stream);
      }
      return thru;
    }, through());
  }
docs: Take all incoming streams combine them into a single through
  stream.  Writing to the returned stream will write to all
  streams passed in.
  
  Handy for chaining writable streams.
  
  @param {...Streams} List of streams to merge
  
  @returns {Stream} Returns a single through stream