Async Generator

Motivated by the Async Generator ES7 proposal https://github.com/jhusain/asyncgenerator

A couple helper functions to bring async support to ES6 generators today:

* asyncIterator: Converts Promise to Promise[].
* asyncPager: Creates a generator function will iterate through a paging function.
* wrapObservable: Creates a generator function by wrapping an observable.

``
npm install async-generator
`

Examples

You'll need to include a polyfill for the regeneratorRuntime such as babel-polyfill

#### asyncIterator: Converts Promise to Promise[].
`typescript
import {asyncIterator} from 'async-generator';

const items: Promise = ...;

for (let promise of asyncIterator(items)) {
const value: number = await promise;

// value will be undefined if the array returned is empty or undefined.
if (value !== undefined) {
doSomething(value);
}
}
`

#### asyncPager: Repeatedly calls a paging function.

`typescript
import {asyncPager} from 'async-generator';

// data consumer
async function getPage(pageNumber: number) {
// ...e.g. web request
return null; // return null/undefined when there are no more pages.
}

for (let promise of asyncPager(getPage)) {
const value: number = await promise;

// value will be undefined if any page is empty.
if (value !== undefined) {
doSomething(value);
}
}
`

#### wrapObservable: Wraps an Observable with an iterator

`typescript
import {wrapObservable} from 'async-generator';

// data consumer
const observable = ...;

for (let promise of wrapObservable(observable)) {
const value: number = await promise;

// value will be undefined if any page is empty.
if (value !== undefined) {
doSomething(value);
}
}
``