Why is this.externals against the rules?

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Flostin(READ BIO)

July 07, 2018 01:51

I have seen many programs using this.externals, but only for basic things like accessing the HTML5 canvas or other small hacks. I've never seen a program use it for evil purposes or anything that could be harmful. This has led me to wonder why this.externals is bad enough to be against the rules.

I once heard that it can be used to load images that are adult rated, but I've never seen such a program attempt this. People could easily bypass this with Bob's Imageinator anyway, or by using shapes to draw something adult rated. My point is that banning this.externals doesn't seem to do anything about adult content. I'm not saying it should, I'm saying that it must be a different reason.

My better guess is that it can be used to load copyrighted images. If a user published a program loading a copyrighted image, Khan Academy would be responsible for it. This does make more sense because Khan Academy has no issue with images on Wikipedia - they are all free to use.

If it is a different reason altogether, feel free to provide corrections.

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Evan Lewis

July 08, 2018 16:56
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Hi Flostin,

Thanks for bringing this up!

this.externals violates our Disallowed Functionality section of our Program Guidelines for PJS programs. Our version of PJS has some features and functionality disabled for site security and performance reasons, which is why we have chosen to disallow users to access externals (window, canvas, localStorage, etc.)

If you're wanting to use things like localStorage or external fonts, you should use the webpage environment. The webpage version of the Program Guidelines do not contain a Disallowed Functionality section. Additionally, basically anything that can be done in the PJS environment can also be done using the webpage environment.

If you have any doubts about whether or not something is allowed or considered to be accessing externals, do it in the webpage environment and then you don't have to worry about getting in trouble. The general rule of thumb is anything that uses this.externals or window.something is not allowed. Also, anything that requires hacky or kludgy code, rather than straightforward JS, to run correctly is likely an external and is not allowed in the PJS environment.

Hope this helps! Let me know if you have any further questions!

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Why is this.externals against the rules?

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