I would suggest to use && instead of &. Though usable, the use of a single & is still discouraged.
https://stackoverflow.com/questions/7310109/whats-the-difference-between-and-in-javascript
Before using length, check the input is really an array. Check MDN Docs
but how i do not get it
Not a kata issue.
returns false for every other input.
Not all input values are arrays (or strings) that have length property. In your case the passed value was null (it's there in the error message).
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I would suggest to use && instead of &. Though usable, the use of a single & is still discouraged.
https://stackoverflow.com/questions/7310109/whats-the-difference-between-and-in-javascript
Before using length, check the input is really an array. Check MDN Docs
but how i do not get it
Not a kata issue.
Not all input values are arrays (or strings) that have length property. In your case the passed value was null (it's there in the error message).
This comment is hidden because it contains spoiler information about the solution