--- /dev/null
+'use strict';
+// https://github.com/tc39/proposal-iterator-helpers
+var $ = require('../internals/export');
+var iterate = require('../internals/iterate');
+var aFunction = require('../internals/a-function');
+var anObject = require('../internals/an-object');
+
+$({ target: 'Iterator', proto: true, real: true }, {
+ reduce: function reduce(reducer /* , initialValue */) {
+ anObject(this);
+ aFunction(reducer);
+ var noInitial = arguments.length < 2;
+ var accumulator = noInitial ? undefined : arguments[1];
+ iterate(this, function (value) {
+ if (noInitial) {
+ noInitial = false;
+ accumulator = value;
+ } else {
+ accumulator = reducer(accumulator, value);
+ }
+ }, undefined, false, true);
+ if (noInitial) throw TypeError('Reduce of empty iterator with no initial value');
+ return accumulator;
+ }
+});