Alternative for array.contains() method

I was using this method in a while ago, but now Unity doesn’t have it in their MonoBehavior. Is there an alternative to this method?

Array.Contains has nothing to do with MonoBehaviour. The JS Array class never had Contains (and JS Arrays should never be used anyway). System.Array doesn’t have Contains unless you use the extension method (requires importing the Linq namespace). Otherwise use Array.IndexOf. Or List.Contains.