Re: Use of CryptoKey with polyfill

W.r.t. 2: "if (window.crypto.subtle) { ... }", right?

On Mon, Jan 12, 2015 at 10:37 PM, Jim Schaad <ietf@augustcellars.com> wrote:

> This may be an issue of ignorance on my part, if it is please excuse me.
>
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> I am currently writing some code and have found that one or more of the
> algorithms that I need for it are not either on the currently supported or
> planned supported list for the browser that I am using.  The way that I
> would normally solve this is by doing polyfill for the missing algorithms.
> In looking at this I have run into a couple of issues that I am not sure
> how to deal with.
>
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>
> 1.       Is it possible to create a script size class which has the
> CryptoKey interface in the prototype chain?  This is one of two issues that
> I have (so far) discovered with the use of “instanceof CryptoKey” as a
> discriminator in writing my library code.  (The second is the fact that
> interfaces which are remoted from a different environment will have this be
> false.)  I have not actually tried to write the correct polyfill for this
> but have not yet found anything that would support it working either.  My
> first guess is that this might be very dependent on how the browser
> implements interfaces.
>
> 2.       If I want the polyfill to be conditional, then the normal
> approach I have seen in the past is to do some type of test on the feature
> and either define or not define the polyfill as appropriate.   I am not
> sure how this is going to work out with a Promises approach to everything.
> Currently the way that I would think about this is to generate a key with
> the algorithm in question.  However given that the result the promise would
> be pending unless the algorithm is not in the dictionary to be
> normalized.   I am also not sure when the promises would be scheduled
> relative to the onload event – would they complete before the onload or
> would they be potentially afterwords.  My assumption is that the timing is
> totally arbitrary.  This means that the polyfill code may need to be called
> and started prior to it finding out if the feature it is filling in for
> actually exists in the base implementation.
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> Help – Jim
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