Let arr be an array.

Create a function unique(arr) that should return an array with unique items of arr.

For instance:

function unique(arr) {
  /* your code */
}

let values = ["Hare", "Krishna", "Hare", "Krishna",
  "Krishna", "Krishna", "Hare", "Hare", ":-O"
];

alert( unique(values) ); // Hare, Krishna, :-O

P.S. Here strings are used, but can be values of any type.

P.P.S. Use Set to store unique values.

Open a sandbox with tests.