2 // https://github.com/tc39/proposal-iterator-helpers
3 var $ = require('../internals/export');
4 var apply = require('../internals/function-apply');
5 var aCallable = require('../internals/a-callable');
6 var anObject = require('../internals/an-object');
7 var createAsyncIteratorProxy = require('../internals/async-iterator-create-proxy');
9 var AsyncIteratorProxy = createAsyncIteratorProxy(function (Promise, args) {
11 var mapper = state.mapper;
13 return Promise.resolve(anObject(apply(state.next, state.iterator, args))).then(function (step) {
14 if (anObject(step).done) {
16 return { done: true, value: undefined };
18 return Promise.resolve(mapper(step.value)).then(function (value) {
19 return { done: false, value: value };
24 $({ target: 'AsyncIterator', proto: true, real: true }, {
25 map: function map(mapper) {
26 return new AsyncIteratorProxy({
27 iterator: anObject(this),
28 mapper: aCallable(mapper)