JavaScript: return an array of unique numbers from an array of numbers using reduce() and find()

JSUniqueNumArrayWithReduceAndFind.js

function makeUnique(array) {
  return array.reduce(function(prev, num) {
    if (!prev.find(function(item) { return item == num; })) { 
      prev.push(num);
    }
    return prev;
  }, []);
}
var uniqueNumbers = makeUnique([1, 6 ,5, 6, 4, 3, 3, 3, 2, 1, 1]);