--- /dev/null
+'use strict';
+// https://github.com/tc39/proposal-iterator-helpers
+var $ = require('../internals/export');
+var aFunction = require('../internals/a-function');
+var anObject = require('../internals/an-object');
+var createIteratorProxy = require('../internals/iterator-create-proxy');
+var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing');
+
+var IteratorProxy = createIteratorProxy(function (arg) {
+ var iterator = this.iterator;
+ var result = anObject(this.next.call(iterator, arg));
+ var done = this.done = !!result.done;
+ if (!done) return callWithSafeIterationClosing(iterator, this.mapper, result.value);
+});
+
+$({ target: 'Iterator', proto: true, real: true }, {
+ map: function map(mapper) {
+ return new IteratorProxy({
+ iterator: anObject(this),
+ mapper: aFunction(mapper)
+ });
+ }
+});