Problem 10. Number as Words / if else

let input = ['253'];

let print = this.print || console.log;
let gets = this.gets || ((arr, index) => () => arr[index++])(input, 0);
//get the input
let stringInput = gets();
//reserve empty string to fill for result
let resultString = '';

//in case in 3 digit string
if (stringInput.length === 3) {
    //get the input by index and convert them to numbers in 3 digit string
    let firstDigitUnique = +stringInput[0];
    let secondDigit = +stringInput[1];
    let thirdDigit = +stringInput[2];
    //write first digit in words
    if (firstDigitUnique === 1) {
        resultString += 'one hundred '
    } else if (firstDigitUnique === 2) {
        resultString += 'two hundred ';
    } else if (firstDigitUnique === 3) {
        resultString += 'three hundred ';
    } else if (firstDigitUnique === 4) {
        resultString += 'four hundred ';
    } else if (firstDigitUnique === 5) {
        resultString += 'five hundred ';
    } else if (firstDigitUnique === 6) {
        resultString += 'six hundred ';
    } else if (firstDigitUnique === 7) {
        resultString += 'seven hundred ';
    } else if (firstDigitUnique === 8) {
        resultString += 'eight hundred ';
    } else if (firstDigitUnique === 9) {
        resultString += 'nine hundred ';
    }
    // in case if second and third index are 0
    if (secondDigit === 0 && thirdDigit === 0) {
        stringInput = '';
    } else {
        resultString += 'and';
        stringInput = secondDigit + '' + thirdDigit;
    }
}
//in case 2 digit string
if (stringInput.length === 2) {
    let num = +stringInput;
    //convert input to number in unique word cases from 1 to 19
    if (num < 20) {
        if (num === 1) {
            resultString += ' one';
        } else if (num === 2) {
            resultString += ' two';
        } else if (num === 3) {
            resultString += ' three';
        } else if (num === 4) {
            resultString += ' four';
        } else if (num === 5) {
            resultString += ' five';
        } else if (num === 6) {
            resultString += ' six';
        } else if (num === 7) {
            resultString += ' seven';
        } else if (num === 8) {
            resultString += ' eight';
        } else if (num === 9) {
            resultString += ' nine';
        } else if (num === 10) {
            resultString += ' ten';
        } else if (num === 11) {
            resultString += ' eleven';
        } else if (num === 12) {
            resultString += ' twelve';
        } else if (num === 13) {
            resultString += ' thirteen';
        } else if (num === 14) {
            resultString += ' fourteen';
        } else if (num === 15) {
            resultString += ' fifteen';
        } else if (num === 16) {
            resultString += ' sixteen';
        } else if (num === 17) {
            resultString = ' seventeen';
        } else if (num === 18) {
            resultString += ' eighteen';
        } else if (num === 19) {
            resultString += ' nineteen';
        }
    } else {
        let firstDigit = +stringInput[0];
        let secondDigit = +stringInput[1];

        if (firstDigit === 2) {
            resultString += ' twenty';
        } else if (firstDigit === 3) {
            resultString += ' thirty';
        } else if (firstDigit === 4) {
            resultString += ' forty';
        } else if (firstDigit === 5) {
            resultString += ' fifty';
        } else if (firstDigit === 6) {
            resultString += ' sixty';
        } else if (firstDigit === 7) {
            resultString += ' seventy';
        } else if (firstDigit === 8) {
            resultString += ' eighty';
        } else if (firstDigit === 9) {
            resultString += ' ninety';
        }
            if (secondDigit === 0) {
                stringInput = '';
            } else {
                stringInput = '' + secondDigit;
            }
    }

}
//in case 1 number string
if (stringInput.length === 1 ) {
    let num = +stringInput;

    if (num === 0) {
        resultString += 'Zero';
    } else if (num === 1) {
        resultString += ' one';
    } else if (num === 2) {
        resultString += ' two';
    } else if (num === 3) {
        resultString += ' three';
    } else if (num === 4) {
        resultString += ' four';
    } else if (num === 5) {
        resultString += ' five';
    } else if (num === 6) {
        resultString += ' six';
    } else if (num === 7) {
        resultString += ' seven';
    } else if (num === 8) {
        resultString += ' eight';
    } else if (num === 9) {
        resultString += ' nine';
    }
}

resultString = resultString.trim();
let firstLetter =  resultString.charAt(0).toUpperCase();
resultString = firstLetter + resultString.substring(1);

console.log(resultString);