export default function unique(arr){
  return Array.from(new Set(arr.sort()));
}

import unique from './js-debug-mutating-input';

describe('unique', () => {
  test('returns unique values in first-seen order', () => {
    expect(unique([2,2,1,3,1])).toEqual([2,1,3]);
  });

  test('does not mutate the caller array', () => {
    const ids = [2,2,1,3,1];
    unique(ids);
    expect(ids).toEqual([2,2,1,3,1]);
  });

  test('does not mutate a shared array reference inside another object', () => {
    const state = { selectedIds: [3,3,2,1] };
    unique(state.selectedIds);
    expect(state.selectedIds).toEqual([3,3,2,1]);
  });
});