Arrays & Array Methods (map, filter, reduce)

const values = ['a', 'b', 'a', 'c', 'b'];
const unique = values.filter((value, index, array) => 
  array.indexOf(value) === index
);

To sort the array
To remove duplicates
This pattern removes duplicates by: 1) indexOf() returns first occurrence index of each value, 2) Comparing with current index identifies unique elements, 3) Only keeps elements where current index matches first occurrence, 4) Maintains original element order, 5) Alternative to using Set for uniqueness, 6) Works with any array element type, 7) More verbose but flexible than Set conversion, 8) Common pattern for array deduplication.
To count occurrences
To reverse the array