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Comment by talles | Hacker News Reader

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talles·

"JSFuck is an esoteric and educational programming style"

How exactly is this educational?

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It teaches you the funky behavior of JavaScript. For instance, `[]["filter"]` returns an empty function called filter.

In order to get particular characters (for example: f), the script uses "false"[0], where "false" is derived from adding ![] + [], and 0 is derived from +[].

Putting all of that together ($ node):

> (![]+[])[+[]]

'f'

Not sure that []["filter"] is all that funky of an example as it's just grabbing the arrays prototype method "filter" using bracket notation.

Here's some better examples of JS oddities: http://stackoverflow.com/q/9032856/1538708

The funkiness is really that []["filter"]["constructor"] is a function that behaves like eval(), or rather, it returns a function that when called executes the string that was passed to the constructor function. That's how they're actually running the code.

> []["filter"]["constructor"]("alert(1)")()

By demonstrating creative abuse of a language, one can better understand what the language constructs do and the scope of their capability.

The comparable IOCCC.org contest is a great place to learn C: sure the primary focus is making obfuscated code, and the audience marvels at the bizarreness thereof, but taking the time to pick a submission apart and figure out why it works (despite a host of reasons why you'd think it shouldn't) expands your understanding of the language.

It's a great way to improve your language skills when you've reached the initial "I know language X" confidence.

I took the 'educational' to mean 'this should never be used in a real application' :)

If someone cogitates to use this for real... it shouldn't be doing it anything at all.

Unless you consider cross-site scripting attacks to be applications.

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