function alphabetSubsequence(str) {
    //  write code here.
    if (str == null || str == undefined || str.length <= 1){
        return true
    }
    // str.length >=2
    let minCode = str.charCodeAt(0)
    for (let i=1; i<str.length; i++){
        if (str.charCodeAt(i)<= minCode){
            return false
        }else{
            minCode = str.charCodeAt(i)
        }
    }
    return true
}



/**
* 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);
    });
});