test Object.create

gistfile1.js

var clone = function( object ) {
  var copied = Object.create( Object.getPrototypeOf( object ) ),
      properties = Object.getOwnPropertyNames( object ),
      index = 0,
      name;
  for ( ; name = properties[ index ]; index++ ){
    Object.defineProperty( copied,
                           name,
                           Object.getOwnPropertyDescriptor( object, name ) );
  }
  return copied;
};

function Tuple1( f, s ){
  this.fst = f;
  this.snd = s;
};

var Tuple2 = function( f, s ){
  this.fst = f;
  this.snd = s;
}

// test by Chrome
var t1 = new Tuple1( 1, 2 );
var t2 = new Tuple2( 1, 2 );

var t1_ = clone( t1 ); // Tuple1
var t2_ = clone( t2 ); // Object (!?)