--- /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 filterer = this.filterer;
+ var next = this.next;
+ var result, done, value;
+ while (true) {
+ result = anObject(next.call(iterator, arg));
+ done = this.done = !!result.done;
+ if (done) return;
+ value = result.value;
+ if (callWithSafeIterationClosing(iterator, filterer, value)) return value;
+ }
+});
+
+$({ target: 'Iterator', proto: true, real: true }, {
+ filter: function filter(filterer) {
+ return new IteratorProxy({
+ iterator: anObject(this),
+ filterer: aFunction(filterer)
+ });
+ }
+});