Re: File API: Blob.type

On Wed, Mar 6, 2013 at 3:22 AM, Anne van Kesteren <> wrote:

> Okay, so given I think
> we should put at least minimal restrictions on Blob's constructor
> concerning Blob.type. We made it "anything goes" because in theory
> with Content-Type anything goes. But of course that is false and we
> should have noticed that at the time. Content-Type's value cannot
> contain CRLF, Content-Type's value is also a byte sequence, not a code
> point sequence, and certainly not a code unit sequence.
> 1. I think we should change the type from DOMString to ByteString,
> just like XMLHttpRequest has it.

Blob.type is a MIME type, not a Content-Type header.  It's a string of
codepoints, not a series of bytes.  XHR is a protocol-level API, so maybe
it makes sense there, but it doesn't make sense for Blob.

WebKit already throws SyntaxError for codepoints outside the ASCII range,
eg. new Blob([], {type: "漢字"}).  This should just be extended to throw for
anything that isn't printable ASCII, which would include CR, LF, and other
control characters (especially nil).  In other words, anything not in the
Unicode range [U+0020,U+007E].

It doesn't look like WebKit's exception is in the spec.  I think this
should be added.

Also, WebKit lowercases the type parameter.  This doesn't seem to be in the
spec.  ( says "ASCII-encoded
string in lower case", but that's non-normative.)  I think it should be.

Glenn Maynard

Received on Wednesday, 6 March 2013 14:22:04 UTC