Blob constructor error message when passing a string is misleading

[Ethan-Arrowood]

Is your feature request related to a problem? Please describe.

Working with the new Blob api. Cannot instantiate using a string though I don't see why not.

new Blob('nodejs')

// -> The "sources" argument must be an instance of Iterable. Received type string ('nodejs')

Describe the solution you'd like

Maybe I'm misunderstanding, but I think strings to implement [Symbol.iterator]; does that not make it an instance of Iterable?

Describe alternatives you've considered

Plenty of work arounds - think this would make for a good addition.

Happy to contribute this feature too

[Ethan-Arrowood]

Oh looks like this is intentionally not supported

node/lib/internal/blob.js

Line 106 in 7919ced

typeof sources === 'string') {

[Ethan-Arrowood]

Can we add a reason why to the docs?

[bl-ue]

#36811

[aduh95]

Here's my interpretation of why a string is not accepted: The specs dictates that the param must be a sequence<BlobPart>. It's not clear to me if the string is interpreted as a USVString (which doesn't seem to be a sequence in that specification), or a DOMString (which is defined as a sequence<unsigned short> and unsigned short is not a BlobPart), but either way new Blob('string') is meant to fail.

Now I agree the error message is misleading, for reference here's the error messages thrown by some browsers:

• Chromium: TypeError: Failed to construct 'Blob': The provided value cannot be converted to a sequence.
• Firefox: TypeError: Blob constructor: Argument 1 can't be converted to a sequence.
• Safari: TypeError: Value is not a sequence

[jasnell]

This works just fine, however: new Blob(['hello'])

[jasnell]

@Ethan-Arrowood ... just as a heads up since you're using Blob... sometime in the next two months as time allows, I will be working on Blob supporting async data sources. It won't impact the API usage at all, but figured it's worthwhile to give a heads up.

[Ethan-Arrowood]

Yes I saw that, very excited for it. I'm using this in undici-fetch and it'll be a nice perf boost if blob can support the async iterator sources directly 😄