Darkhogg/polyethylene

# Polyethylene

Polyethylene is a wrapping layer around iterators and async iterators that lets you chain
functional operators in a similar way you do with arrays but without the memory overhead or having
to wait for an asynchronous iteration to end.

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## 2.0 Changes

  - **Breaking Changes**
    - Move to ESModules and remove support for CommonJS
    - Split `Poly.from` into `Poly.syncFrom` and `Poly.asyncFrom`
    - Split `Poly.iterate` into `Poly.syncIterate` and `Poly.asyncIterate`
    - Remove `options` object altogether (replaced with `prefetch` method)
    - Remove default arguments for most methods that accept a function as a parameter (`unique` and `sort` preserve their defaults)
    - Rename `group` and `groupWhile` to `chunk` and `chunkWhile` respectively
    - Rename `drain` to `complete`
  - **New Features**
    - Port codebase to TypeScript, and add type definition files
    - Add `Poly.empty<T>` method to create (typed) empty iterables
    - Add `prefetch` method to async iterables
    - Add `filterNotNullish` as a shorthand for filtering out `null` and `undefined` from an iterable
    - Add `groupBy` to both sync and async iterables
    - Add `toMap` leaf method to both sync and async iterables
    - Add `toPartitionArray` leaf method to both sync and async iterables

## Example

```typescript
import Poly from 'polyethylene';
import {findUsers, findUserPosts} from 'some-api-lib'

// Print the first 10 posts of each user
await Poly.asyncFrom(findUsers())
  .map(user => Poly.from(findUserPosts(user)).take(10))
  .flat()
  .forEach(post => console.log(post));
```


## Documentation

See the [API Documentation][docs].

  - [docs]: ./blob/master/docs/polyathylene.md


## License
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