Description has changed too much so it only applies to Python.
Perhaps you can find a way so that python specific advice (such as sub-classing int) only shows up for Python code?

I think the ES2015 support via "babel" has broken this test (functions get reformatted by babel).

Looks like ES2015 may have broken this, because newlines and semicolons are inserted into function definitions.

Description should have a cofeescript version of the code sample:

```coffeescript

arr1 = [1, 2, 2, 3, 4]
arr2 = [2, 1, 2, 4, 3]
arr3 = [1, 2, 3, 4]
arr4 = [1, 2, 3, "4"]

arraysSimilar(arr1, arr2) # Should equal true
arraysSimilar(arr2, arr3) # Should equal false
arraysSimilar(arr3, arr4) # Should equal false

```

I keep getting the message "Process was terminated. It took longer than 10000ms to complete".
Do I need to install Java 8 Plugin on my Browser or check back when the servers are less busy?

Looks like the example code does not work for the CoffeeScript verion:
return n if n is < 2
instead of
return n if n < 2

Sorry, originally I was going to have toString return "FF" and toJSON return "0xFF".

Will fix and re-run example test cases to make sure they still work after my changes.

Description needs improvement.
once(console.log) is unbound so will not work in all browsers.

This would be better:

function id(x) { return x; }
logOnce = once(id)
logOnce("foo") // -> "foo"
logOnce("bar") // -> undefined