var finalRomanNumber = [];
var convertedElement = "";
var threeDigitNumber = "";
var fourDigitNumber = "";

function convertToRomanNumberal(num){

    var convertedNumber = num.toString();

    convertedNumber = convertedNumber.split('');
    var digits = convertedNumber.length;
    if(digits > 4){
        alert('Please insert a number that is composed of maximum 4 digits');
    } else {

            if(digits === 1) {
                for(var i = 1; i <= convertedNumber ; i++) {
                     convertedElement += 'I';
                    if(i === 4) {
                        convertedElement = 'IV';
                    } else if( i === 5) {
                        convertedElement = "V";
                    } else if(i === 9) {
                        convertedElement = 'IX';
                    }

                }
            } else if (digits === 2) {
                lastTwoDigitLoop(0,1);

            } else if (digits === 3) {

                lastThreeDigitsLoop(0,1,2);

            } else if ( digits === 4) {
                //alert an error message if the first digit in the number is greater than 4
                if(convertedNumber[0] > 4) {
                        alert(convertedNumber.join('') + ' is not valid. Please try with a lower number(e.g. highest number is : 4999). ');
                    }
                for(var i = 1; i <= convertedNumber[0]; i++) {
                    fourDigitNumber += 'M';
                }
                lastThreeDigitsLoop(1,2,3);
                fourDigitNumber += convertedElement;
                convertedElement = fourDigitNumber;
            }
    }

    //function that loops and slices the string, forming the coresponding Roman Numerals  for the last two digits in a number
    function lastTwoDigitLoop(firstIndex, secondIndex){

            for(var j = 1; j <= convertedNumber[firstIndex]; j++){
                    convertedElement += 'X';
                     if(j === 4) {
                        convertedElement = 'XL';
                    } else if( j === 5) {
                        convertedElement = "L";
                    } else if( j > 9 ){
                        convertedElement+='X';
                    } else if(j === 9) {
                        convertedElement = 'XC';
                    }
             }

                 for(var k = 1; k <=convertedNumber[secondIndex]; k++) {
                    convertedElement += 'I';
                    if (k === 4) {
                        convertedElement = convertedElement.slice(0, -4);
                        convertedElement += 'IV';
                    }
                     else if ( k === 5 ) {
                         convertedElement = convertedElement.slice(0, -3);
                        convertedElement += 'V';
                    } else if( k === 9) {
                        convertedElement = convertedElement.slice(0, -5);
                    convertedElement += 'IX';
                    }
                }
    }
    function lastThreeDigitsLoop(firstDigitIndex, secondDigitIndex, thirdDigitIndex) {
        for(var i = 1; i <= convertedNumber[firstDigitIndex]; i++) {

                    threeDigitNumber += 'C';
                    if( i === 4) {
                        threeDigitNumber = 'CD';
                    } else if(i === 5) {
                        threeDigitNumber = 'D';
                    } else if(i === 9) {
                        threeDigitNumber = 'CM'
                    }

                }
                    lastTwoDigitLoop(secondDigitIndex,thirdDigitIndex);
                     threeDigitNumber += convertedElement;
                    convertedElement = threeDigitNumber;


    }
    //this will be the end result that will be the output in the console
    console.log(convertedElement);

}

convertToRomanNumberal(4989);