Re: [dom] Is it recommended to use Node.getFeature() or Node.isSupported()?

On Thu, 22 Aug 2013 10:03:34 +0200, David Bruant <>  

> Le 22/08/2013 04:11, Tab Atkins Jr. a écrit :
>> On Wed, Aug 21, 2013 at 5:56 PM, Boris Zbarsky <> wrote:
>>> On 8/21/13 8:43 PM, James Craig wrote:
>>>> if (typeof document.body.ondismissrequest !== "undefined") {
>>> Just if ("ondismissrequest" in document.body), I'd think.
> I could not agree more :-)
>> Yeah, this is all you need to do.  It's not perfect, but web devs are
>> good at making a racket when we accidentally ship something that
>> passes this test but doesn't actually work.
> Unfortunately indeed.
> This reminds me of discussions related to FirefoxOS (when some features,  
> disabled for security reasons are exposed as null [1]).
> Also reminds me of a comment I read from the Persona project [2]
> Maybe specs (WebIDL?) should start providing guidance on how not to  
> expose an API when it doesn't work (disabled for security reason or  
> else)?

When support for a feature is disabled (e.g. as an emergency measure to  
mitigate a security problem, or to aid in development, or for performance  
reasons), user agents must act as if they had no support for the feature  
whatsoever, and as if the feature was not mentioned in this specification.  
For example, if a particular feature is accessed via an attribute in a Web  
IDL interface, the attribute itself would be omitted from the objects that  
implement that interface — leaving the attribute on the object but making  
it return null or throw an exception is insufficient.

Simon Pieters
Opera Software

Received on Thursday, 22 August 2013 09:31:39 UTC