| 'use strict'; | 
| var anObject = require('../internals/an-object'); | 
| var aConstructor = require('../internals/a-constructor'); | 
| var isNullOrUndefined = require('../internals/is-null-or-undefined'); | 
| var wellKnownSymbol = require('../internals/well-known-symbol'); | 
|   | 
| var SPECIES = wellKnownSymbol('species'); | 
|   | 
| // `SpeciesConstructor` abstract operation | 
| // https://tc39.es/ecma262/#sec-speciesconstructor | 
| module.exports = function (O, defaultConstructor) { | 
|   var C = anObject(O).constructor; | 
|   var S; | 
|   return C === undefined || isNullOrUndefined(S = anObject(C)[SPECIES]) ? defaultConstructor : aConstructor(S); | 
| }; |