function alphabetSubsequence(str) {
    //  write code here.
    orderCheck = () => {
        //loops through original string returning true if next character is greater than last alphabetically
        const alphabet = "abcdefghijklmnopqrstuvwxyz";
        //initialise result as true
        let result = true;
        //loop through each character (except last as nothing to compare against next)
        for( let i = 0; i <= str.length -2; i++){
            //easier names for current and next item
            let currentCharIndex = alphabet.indexOf(str[i])
            let nextCharIndex = alphabet.indexOf(str[i+1])
            
            //return false if next item is not greater than current item
            if ( nextCharIndex <= currentCharIndex){
                result = false;
                break;
            }
        }
        return result;
    }
    
    
    duplicateCheck = () => {
        //creates new set (unique) and returns true if set size is smaller than str length
        const uniqueChars = new Set(str);
        return str.length > uniqueChars.size? true: false;
    }
    
    //returns true if both checks are correct (duplicate check should be false)
    return orderCheck() && (!duplicateCheck()) ? true : false;
}

/**
* 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 when no 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);
    });
});