[guide] Rejections Should Be Errors should cater for DOMException

[marcoscaceres]

The advice given in the error section is a bit problematic, as DOM recommends using DOMExceptions, which are not instances of ES Error :( I agree that we should Error instead, but there is a lot precedence for using DOMException on the platform.

[marcoscaceres]

updated issue title.

[erights]

@marcoscaceres Where is this advice?

[domenic]

Actually DOMException is instanceof Error; it's DOMError that's the problem. But yes, we should specifically tell people not to use DOMError, and instead to use DOMException.

[marcoscaceres]

@erights it's not quite explicit in the spec, but basically: http://dom.spec.whatwg.org/#errors

@domenic see: http://dom.spec.whatwg.org/#domexception ... it does not extend Error.

[domenic]

Oh poop. Well, in that case, neither DOMError nor DOMException is currently suitable for use with promises.

[domenic]

/cc @annevk @sicking

[marcoscaceres]

The test:

try{document.body.appendChild(document.body)}catch(e){ e instanceof Error }

Chrome: true
Firefox: false
Safari: true

[annevk]

DOMException has problems, this is not one of them. DOMError is planned for removal.

[marcoscaceres]

Yeah, turned out that WebIDL defines what the prototype is. It's still very messy the way it's defined and Anne filed a bug for this long ago. Sorry for the wild goose chase.