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- 'use strict';
- // https://github.com/tc39/proposal-iterator-helpers
- var $ = require('../internals/export');
- var global = require('../internals/global');
- var call = require('../internals/function-call');
- var aCallable = require('../internals/a-callable');
- var anObject = require('../internals/an-object');
- var getIteratorMethod = require('../internals/get-iterator-method');
- var createIteratorProxy = require('../internals/iterator-create-proxy');
- var iteratorClose = require('../internals/iterator-close');
- var TypeError = global.TypeError;
- var IteratorProxy = createIteratorProxy(function () {
- var iterator = this.iterator;
- var mapper = this.mapper;
- var result, mapped, iteratorMethod, innerIterator;
- while (true) {
- try {
- if (innerIterator = this.innerIterator) {
- result = anObject(call(this.innerNext, innerIterator));
- if (!result.done) return result.value;
- this.innerIterator = this.innerNext = null;
- }
- result = anObject(call(this.next, iterator));
- if (this.done = !!result.done) return;
- mapped = mapper(result.value);
- iteratorMethod = getIteratorMethod(mapped);
- if (!iteratorMethod) {
- throw TypeError('.flatMap callback should return an iterable object');
- }
- this.innerIterator = innerIterator = anObject(call(iteratorMethod, mapped));
- this.innerNext = aCallable(innerIterator.next);
- } catch (error) {
- iteratorClose(iterator, 'throw', error);
- }
- }
- });
- $({ target: 'Iterator', proto: true, real: true, forced: true }, {
- flatMap: function flatMap(mapper) {
- return new IteratorProxy({
- iterator: anObject(this),
- mapper: aCallable(mapper),
- innerIterator: null,
- innerNext: null
- });
- }
- });
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