--- /dev/null
+var classof = require('../internals/classof');
+var Iterators = require('../internals/iterators');
+var wellKnownSymbol = require('../internals/well-known-symbol');
+
+var ITERATOR = wellKnownSymbol('iterator');
+
+module.exports = function (it) {
+ if (it != undefined) return it[ITERATOR]
+ || it['@@iterator']
+ || Iterators[classof(it)];
+};