stream-to-async-iterator

Stream To Async Iterator

Overview

stream-to-async-iterator provides a wrapper that implements Symbol.asyncIterator. This will allow streams to be usable as async iterables that can be used in for-await-of loops.

Supports node.js 12 and up.

Installation

With NPM:

npm install stream-to-async-iterator

With Yarn:

yarn add stream-to-async-iterator

The included examples use async/await syntax for for-of loops. This assumes you are in an environment that natively supports this new syntax, or that you use a tool such as Babel. In addition, for async iterators to work properly, the Symbol.asyncIterator symbol must be defined. Core-js can help with that.

Usage

Import the StreamToAsyncIterator class and pass the stream to its constructor. The iterator instance can be directly used in for-of contexts.

If the stream is in object mode, each iteration will produce the next object. See the node documentation for more information.

#!/usr/bin/env node
"use strict";
const { Readable } = require("stream");
const S2A = require("../").default;

(async function () {
    const readStream = Readable.from([1, 2, 3]);
    for await (const chunk of new S2A(readStream)) {
        console.dir({ chunk });
    }
})();

Outputs:

{ chunk: 1 }
{ chunk: 2 }
{ chunk: 3 }

References

• https://github.com/tc39/proposal-async-iteration
• https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-async-generator-functions

Changelog

v1.0.0

• Breaking Change: Dropping support for Node 11 and below.
• Breaking Change: Dropping support for Flow.
• Bug Fix: Resolves #5. Event handlers are cleaned up after each iteration, fixing some memory leak issues.
• Bug Fix: Resolves #7. Code no longer depends on babel runtimes or regenerator.
• Bug Fix: Handles stream not buffering due to starving the event loop.
• Feature: Resolves #1. Now handles .throw and .return hooks on the async iterator.
• Feature: Properly closes stream when finished.
• Feature: Added support for TypeScript.
• Feature: Support for Node.js versions 12, 14, and 16.
• Chore: General overhaul of project setup (should not impact what is published).