@sec-ant/readable-stream

A tiny, zero-dependency yet spec-compliant asynchronous iterator polyfill/ponyfill for ReadableStreams.

Features

Asynchronously iterate a ReadableStream

With this package, you can consume a ReadableStream as an AsyncIterable.

• spec: https://streams.spec.whatwg.org/#rs-asynciterator
• tests: https://github.com/Sec-ant/readable-stream/blob/main/tests/asyncIterator.spec.ts (copied from wpt)

Convert an AsyncIterable or an Iterable into a ReadableStream

With this package, you can construct a ReadableStream from an AsyncIterable or an Iterable.

• spec: https://streams.spec.whatwg.org/#rs-from
• tests: https://github.com/Sec-ant/readable-stream/blob/main/tests/fromAnyIterable.spec.ts (copied from wpt)

This package passes all the aforementioned tests.

Install

npm i @sec-ant/readable-stream

Usage

Ponyfill

This package can be imported as a ponyfill to avoid side effects:

asyncIterator

Path:

@sec-ant/readable-stream/ponyfill/asyncIterator

Example:

import {
  asyncIterator,
  type ReadableStreamIteratorOptions,
} from "@sec-ant/readable-stream/ponyfill/asyncIterator";

const readableStream = (await fetch("https://www.example.org/")).body;

let total = 0;
for await (const chunk of asyncIterator.call(readableStream)) {
  total += chunk.length;
}

console.log(total);

Check https://streams.spec.whatwg.org/#rs-class-definition and https://streams.spec.whatwg.org/#rs-asynciterator for further explanation on ReadableStreamIteratorOptions.

fromAnyIterable

Path:

@sec-ant/readable-stream/ponyfill/fromAnyIterable

Example:

import { fromAnyIterable } from "@sec-ant/readable-stream/ponyfill/fromAnyIterable";

const readableStream = fromAnyIterable(["a", "b"]);

All-in-One

Path:

@sec-ant/readable-stream/ponyfill

Example:

import {
  fromAnyIterable,
  asyncIterator,
  type ReadableStreamIteratorOptions,
} from "@sec-ant/readable-stream/ponyfill";

Polyfill

This package can be imported as a drop-in polyfill with side effects.

ReadableStream.prototype[Symbol.asyncIterator] and ReadableStream.prototype.values

Path:

@sec-ant/readable-stream/polyfill/asyncIterator

Example:

import "@sec-ant/readable-stream/polyfill/asyncIterator";

const readableStream = (await fetch("https://www.example.org/")).body;

let total = 0;
for await (const chunk of readableStream) {
  total += chunk.length;
}

console.log(total);

ReadableStream.from

Path:

@sec-ant/readable-stream/polyfill/fromAnyIterable

Example:

import "@sec-ant/readable-stream/polyfill/fromAnyIterable";

const readableStream = ReadableStream.from(["a", "b"]);

Note that ReadableStream.from is not typed because declared vars cannot be overridden.

All-in-One

Path:

@sec-ant/readable-stream/polyfill

Example:

import "@sec-ant/readable-stream/polyfill";

Ponyfill + Polyfill

asyncIterator

Path:

@sec-ant/readable-stream/asyncIterator

Example:

import {
  asyncIterator,
  type ReadableStreamIteratorOptions,
} from "@sec-ant/readable-stream/asyncIterator";
// also with side effects

fromAnyIterable

Path:

@sec-ant/readable-stream/fromAnyIterable

Example:

import { fromAnyIterable } from "@sec-ant/readable-stream/fromAnyIterable";
// also with side effects

All-in-One

Path:

@sec-ant/readable-stream

Example:

import {
  fromAnyIterable,
  asyncIterator,
  type ReadableStreamIteratorOptions,
} from "@sec-ant/readable-stream";
// also with side effects

Types

You can also use this package to augment the ReadableStream type for async iteration if the runtime already supports it but the type system does not.

Path:

@sec-ant/readable-stream/async-iterator

Example:

/// <reference types="@sec-ant/readable-stream/async-iterator" />

License

MIT