// const alphabetSubsequence = str => 
//   str === [...new Set(str.split('')
//                          .sort((a, b) => 
//                            a.charCodeAt(0) - b.charCodeAt(0)
//                          )
//                      )
//           ].join('')
// const alphabetSubsequence = str => 
//   str === [...new Set(str.split('')
//                          .sort((a, b) => 
//                            a.localeCompare(b)
//                          )
//                      )
//           ].join('')
// const alphabetSubsequence = str => 
//   str === [...new Set(str.split('')
//                          .sort((a, b) => 
//                            a > b 
//                              ? 1 
//                              : a < b 
//                                ? -1 
//                                : 0))]
//                          .join('')
const alphabetSubsequence = str => 
  str === str.split('')
             .reduce((arr, c) => 
               !!~arr.indexOf(c) 
                 ? arr 
                 : arr.concat([c]), [])
             .sort((a, b) => a.localeCompare(b))
             .join('')



/**
* Test Suite 
*/
describe('alphabetSubsequence()', () => {
    it('returns false when it has duplicate letters', () => {
        // arrange
        const str = 'effg';
        
        // act
        const result = alphabetSubsequence(str);

        // log
        console.log("result 1: ", result);
        
        // assert
        expect(result).toBe(false);
    });

    it('returns false when NOT in ascending a - z order', () => {
        // arrange
        const str = 'cdce';
        
        // act
        const result = alphabetSubsequence(str);

        // log
        console.log("result 2: ", result);
        
        // assert
        expect(result).toBe(false);
    });
    
    it('returns true whenno duplicates and is ascending a - z order ', () => {
        // arrange
        const str = 'ace';
        
        // act
        const result = alphabetSubsequence(str);

        // log
        console.log("result 3: ", result);
        
        // assert
        expect(result).toBe(true);
    });
});