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Blob constructor error message when passing a string is misleading #38856
Description
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
Activity
Ethan-Arrowood commentedon May 30, 2021
Oh looks like this is intentionally not supported
node/lib/internal/blob.js
Line 106 in 7919ced
Ethan-Arrowood commentedon May 30, 2021
Can we add a reason why to the docs?
bl-ue commentedon May 30, 2021
#36811
aduh95 commentedon May 30, 2021
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 aUSVString(which doesn't seem to be a sequence in that specification), or aDOMString(which is defined as asequence<unsigned short>andunsigned shortis not aBlobPart), but either waynew 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:
TypeError: Failed to construct 'Blob': The provided value cannot be converted to a sequence.TypeError: Blob constructor: Argument 1 can't be converted to a sequence.TypeError: Value is not a sequencejasnell commentedon May 31, 2021
This works just fine, however:
new Blob(['hello'])jasnell commentedon May 31, 2021
@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 onBlobsupporting async data sources. It won't impact the API usage at all, but figured it's worthwhile to give a heads up.Ethan-Arrowood commentedon May 31, 2021
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 😄
[-]Support string as source for Blob[/-][+]Blob constructor error message when passing a string is misleading[/+]buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string
buffer: improve Blob constructor error message when passing a string