Path: csiph.com!aioe.org!news.mb-net.net!open-news-network.org!.POSTED.214.226.197.178.dynamic.wless.zhbmb00p-cgnat.res.cust.swisscom.ch!not-for-mail
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Object.create(canvas.getContext())
Date: Sun, 12 Nov 2017 17:42:35 +0100
Organization: PointedEars Software (PES)
Lines: 34
Message-ID: <5326256.lOV4Wx5bFT@PointedEars.de>
References: <ou96ju$mvd$1@gwaiyur.mb-net.net>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8Bit
Injection-Info: gwaiyur.mb-net.net; posting-host="214.226.197.178.dynamic.wless.zhbmb00p-cgnat.res.cust.swisscom.ch:178.197.226.214"; logging-data="18418"; mail-complaints-to="abuse@open-news-network.org"
User-Agent: KNode/4.14.2
X-Face: %i>XG-yXR'\"2P/C_aO%~;2o~?g0pPKmbOw^=NT`tprDEf++D.m7"}HW6.#=U:?2GGctkL,f89@H46O$ASoW&?s}.k+&.<b';Md8`dH6iqhT)6C^.Px|[=M@7=Ik[_w<%n1Up"LPQNu2m8|L!/3iby{-]A+#YE}Kl{Cw$\U!kD%K}\2jz"QQP6Uqr],./"?;=4v
X-User-ID: U2FsdGVkX18yCrQvsnQSP11vJaL66AqH+eFKKeFfpOokuIIub5LApQ==
Cancel-Lock: sha1:0JE2v8f5iTIwqDqz2QlY3/X8aY8=
Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAGFBMVEXTxa4RFk5dUWANED8PFEfy7+MGBiW+n3ZNF/QuAAACaElEQVQ4jVXUwVOcMBQG8Dc7Rc4PUntdWV2uxjDpGaGeozOp1woar4jd5t/v9wLstMwsA/ntlxdCAgUc1hjTc9/JCZfGoo3wG3HdmdAWrIJRHe7GM/TmpY5VFefuVcAkkPbLIaN8rmPmjloyZxgyR3GuJ4K0AGtJ2htz8o7yqikm759fldQXaMpbDzjKAG+8v+AugVTOPO5DOjLvGtUYQwh0CPjnVMyGd+8/GfUB5nLKJDD2aLDh5HYyMDJGDwQIo2ZmZcKbowNmAdB/AzyFhrmF2MHRb0QJJfaAnwGB6orZhoykLzJtGwF/xpYxI1dswomiUj3gTuAIqCn/4C7cULwGNBtwMTk3Y4LfKB5YUaOKBKYtpplm7u0vip8tU1NWWyI/7XdcSuIDoMt6rVHMWT0DbjHPGqDqZVSa6zleLcUTcIKLoMv3ueJluALtAo9B302zPPlrtiVScRdCjXvVh3e3JpYa/jjkuC9N+LrBMlz/eAN4eQijX2EdLo6c5tGGHwLyHFtXk89dDGHwCVhG9T0S/j55AhRZgkMCmUQXJ49TnS1wnQDvw0eAh9ICeMmEFbCnPMFzjAvsWoEWEFdYEx+S0MoUZ1gT1wId8+AF3Bl2OoEu906AUHx5VLw/gXYg/x84loOah/2UYNrgiwSwGO7RfUzVBbx/kgpckumGOi6QirtD6gkLTitbnxNol47S2jVc2vsN5kPqaAHT8uUdAJM4v/DanjYOwmUjWznGfwB7sGtAtor5BgofDuzaRj4kSQAqDakTsKORa3Q3xKi3gE1fhl71KRMqrdZ2AWNNg/YOhQyrVBnb+i+nEg4bsDA+egAAAABJRU5ErkJggg==
Xref: csiph.com comp.lang.javascript:34321

Jan Bruns wrote:

> My intention was to create an object that inherits from a specific webgl
> context, so that I can populate some (more or less) webgl-related, app-
> specific helper functions.
> 
> 
>   gl = Object.create( webglcanvas.getContext("webgl2") );
> 
>   dolog(gl);  // prints "[object Object]"
> 
>   dolog(gl.__proto__); // prints "[object WebGL2RenderingContext]"
> 
>   gl.clearColor(0.7, 0.7, 0.7, 1.0);
> 
> 
> TypeError: 'clearColor' called on an object that does not implement
> interface WebGL2RenderingContext.

dolog() is not a built-in function in any ECMAScript implementations that
I know.  That leaves one to *guess* what *your* dolog(…) does (presumably, 
“({}).toString.call(…)”.)

That you can create an object which inherits from another does not mean that 
you can use it like the other; this is particulary true of host objects as 
this one.  If subclassing does not work either (or cannot be assumed to be 
available), create a wrapper object.  If available, you can use “Proxy” 
(ECMAScript 2015+) or “__noSuchMethod__” (Mozilla JavaScript 43+ only, 
obsolete) to implement seamless access.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.