--- /dev/null
+'use strict';
+// https://github.com/tc39/proposal-iterator-helpers
+var $ = require('../internals/export');
+var anObject = require('../internals/an-object');
+var toPositiveInteger = require('../internals/to-positive-integer');
+var createAsyncIteratorProxy = require('../internals/async-iterator-create-proxy');
+
+var AsyncIteratorProxy = createAsyncIteratorProxy(function (arg, Promise) {
+ var state = this;
+
+ return new Promise(function (resolve, reject) {
+ var loop = function () {
+ try {
+ Promise.resolve(
+ anObject(state.next.call(state.iterator, state.remaining ? undefined : arg))
+ ).then(function (step) {
+ try {
+ if (anObject(step).done) {
+ state.done = true;
+ resolve({ done: true, value: undefined });
+ } else if (state.remaining) {
+ state.remaining--;
+ loop();
+ } else resolve({ done: false, value: step.value });
+ } catch (err) { reject(err); }
+ }, reject);
+ } catch (error) { reject(error); }
+ };
+
+ loop();
+ });
+});
+
+$({ target: 'AsyncIterator', proto: true, real: true }, {
+ drop: function drop(limit) {
+ return new AsyncIteratorProxy({
+ iterator: anObject(this),
+ remaining: toPositiveInteger(limit)
+ });
+ }
+});