Re: Object.create(canvas.getContext())

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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)
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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.

Thread

Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-12 10:09 +0000
  Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-12 17:42 +0100
    Re: Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-14 11:48 +0000
      Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-15 02:32 +0100
        Re: Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-17 20:25 +0000
          Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-19 05:48 +0100
            Re: Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-19 21:39 +0000
              Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-19 23:34 +0100
                Re: Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-20 14:47 +0000
                Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-21 04:07 +0100
                Re: Object.create(canvas.getContext()) Jan Bruns <ebay@abnuto.de> - 2017-11-21 16:23 +0000
                Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-22 04:12 +0100
  Re: Object.create(canvas.getContext()) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-11-12 18:45 +0100

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