If the code is correct, then it will. Just try it.

oh ,understood. So ,if i change it to return ,will site approve task?

What happens when you do this in your VS Code:

console.info('My solution returned: ' + duplicateEncode("din"))

Maybe because there is no return keyword in your code at all? console.log and return are different.

idk why it doesnt retern anything ,cause when i wrote in on VS Code it worked

Or maybe just post the code using proper code formatting?

After copying all your code, the answer is still the same: your solution does not return anything.

copy all in my message ,after "Вот сам код :"

Your code doesn't return anything.