There isn't, by design. You write _some_ black-box implementation locally which outputs a textual solution you drop into the browser (at least, this is how it was in 2015 when AoC started).
I can't recommend this enough. I had to miss out on last year's challenges, but planning on participating this year; it's a great way to keep your brain nimble if you feel like you're in a rut.
I can't recommend this enough. I had to miss out on last year's challenges, but planning on participating this year; it's a great way to keep your brain nimble if you feel like you're in a rut.