got it, thanks

Your code is mutating the input, and you're printing it after it was mutated, print it before doing anything else.

When testing (javascript) I got this error for [3,2,1], expected 0 but got 1, isn't it supposed to return index 1 because 2 is the number that fits between 1 and 3? Also for [3.2,2.1,1.4] expected 0 but isn't 2.1 between 3.2 and 1.4?

There are a few problems:

• There is a test with input = null, and you are trying to access .length on it, which crashes the program. You can console log input on codewars too.
• You cannot compare arrays like you're trying. Even [] === [] is false.
• Not a big deal, but using .unshift is very slow. There are better methods out there.

Can anyone tell me what this error means?

"TypeError: Cannot read properties of null (reading 'length')
at countPositivesSumNegatives (test.js:6:14)
at Context.<anonymous> (test.js:36:18)
at process.processImmediate (node:internal/timers:471:21)
expected [ +0, +0 ] to deeply equal []"

when I console log my code it passes the tests with both 0 and empty array but in here I get this error

Yes, you are absolutely right