We can use
indexOf method to do that.
indexOf, we'll expect integer output. Returned value -1 (negative one) is to tell that the item isn't present in the array.
In latest version of ECMA (latest browsers), we can use
includes, we'll expect boolean output (true / false).
For jQuery, we can use
Well, the phrase itself, "check if item in list", then we can use
in operator to do that.
Using that method, we'll expect boolean output (True / False).