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- 'use strict';
- // https://github.com/tc39/proposal-iterator-helpers
- var $ = require('../internals/export');
- var iterate = require('../internals/iterate');
- var aCallable = require('../internals/a-callable');
- var getIteratorDirect = require('../internals/get-iterator-direct');
- var $TypeError = TypeError;
- $({ target: 'Iterator', proto: true, real: true, forced: true }, {
- reduce: function reduce(reducer /* , initialValue */) {
- var record = getIteratorDirect(this);
- aCallable(reducer);
- var noInitial = arguments.length < 2;
- var accumulator = noInitial ? undefined : arguments[1];
- var counter = 0;
- iterate(record, function (value) {
- if (noInitial) {
- noInitial = false;
- accumulator = value;
- } else {
- accumulator = reducer(accumulator, value, counter);
- }
- counter++;
- }, { IS_RECORD: true });
- if (noInitial) throw $TypeError('Reduce of empty iterator with no initial value');
- return accumulator;
- }
- });
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