code: function(original, length){                                                                // 16
    var C;                                                                                             // 17
    if(isArray(original) && isObject(C = original.constructor)){                                       // 18
      C = C[SPECIES];                                                                                  // 19
      if(C === null)C = undefined;                                                                     // 20
    } return new(C === undefined ? Array : C)(length);                                                 // 21
  }
docs: 14 9.4.2.3 ArraySpeciesCreate(originalArray, length)                                                 // 15