ReadableStream is not a subtype of AsyncIterator

[spencerwilson]

🔎 Search Terms

• ReadableStream

🕗 Version & Regression Information

I'm using 5.3.2.

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about ReadableStream/differences in environments

⏯ Playground Link

No response

💻 Code

const rs: AsyncIterable<Uint8Array> = new ReadableStream<Uint8Array>();

🙁 Actual behavior

tsc reports the following error:

Property '[Symbol.asyncIterator]' is missing in type 'ReadableStream<Uint8Array>' but required in type 'AsyncIterable<Uint8Array>'.

That property should not have been missing in ReadableStream.

🙂 Expected behavior

No error, because the Streams WHATWG Living Standard documents that ReadableStream is an async iterable: https://streams.spec.whatwg.org/#rs-asynciterator

Additional information about the issue

Admittedly, this isn't widely supported. At time of writing, it may be that just 3 runtimes support it:

Live data: https://caniuse.com/mdn-api_readablestream_--asynciterator

Note: The browser-compat-data calls this feature "experimental", but I'm not sure what the basis for that is. See mdn/browser-compat-data#22676 h/t @fatcerberus for explaining this classification

[fatcerberus]

Kind of interesting that Node.js supports it since 16.5.0 (July 2021) but Chrome apparently doesn't support it at all, especially since both use V8...

Most likely it's marked experimental because it's only supported by one browser engine (Firefox). Node.js and Deno are not browsers.

[Jamesernator]

Kind of interesting that Node.js supports it since 16.5.0 (July 2021) but Chrome apparently doesn't support it at all

It will be available in the next version of Chrome.

[MartinJohns]

Duplicate of microsoft/TypeScript-DOM-lib-generator#1677.

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.