SOURCE

function foo(arr) {
  let newArr = arr.toString().split(",");
  let set = new Set(newArr);
  let a = Array.from(set);
  return a;
}
let x = foo([[1, 3, 2, 1], [5, 3, 4], [6, 2, 8, 9], 1, 4, 7]);
console.log(x);