Convert the given number into a roman numeral.

roman-numeral-converter.js

const symbols = {
        '1': 'I',
        '5' : 'V',
        '10' : 'X',
        '50' : 'L',
        '100' : 'C',
        '500' :  'D',
        '1000' : 'M'
};

function convertToRoman(num) {
    const digits = num.toString().split('').reverse();
    const numLength = digits.length;

    let romanNum = [];
    for(let i = 0; i < numLength; i += 1){
        if(digits[i] == 0){
            continue;
        }
        switch(i){
            case 0: 
                romanNum.push(convertSingleDigit(digits[i]));
            break;

            case 1:
                romanNum.push(convert2DigitNum(digits[i]));
                break;
            case 2:
                romanNum.push(convert3DigitNum(digits[i]));
                break;
            default:
                romanNum.push(convert4DigitNum(digits[i]));
                break;
        }
        
    }
    return romanNum.reverse().join('');
}

function convertSingleDigit(num){
    if(num > 0 && num < 4){
        return symbols['1'].repeat(num);
    }
    if(num == 4){
        return symbols['1']+symbols['5'];
    }
    if(num == 5){
        return symbols['5'];
    }
    if(num == 6){
        return symbols['5']+symbols['1'];
    }
    if(num > 5 && num < 9){
        return symbols['5'] + (symbols['1'].repeat(num%5));
    }
    if(num == 9){
        return symbols['1']+ symbols['10']
    }
}

function convert2DigitNum(num){
    if(num > 0 && num < 4){
        return symbols['10'].repeat(num);
    }
    if(num == 4){
        return symbols['10']+symbols['50'];
    }
    if(num == 5){
        return symbols['50'];
    }
    if(num == 6){
        return symbols['50']+symbols['10'];
    }
    if(num > 5 && num < 9){
        return symbols['50'] + (symbols['10'].repeat(num%5));
    }
    if(num == 9){
        return symbols['10']+ symbols['100']
    }
}

function convert3DigitNum(num){
    if(num > 0 && num < 4){
        return symbols['100'].repeat(num);
    }
    if(num == 4){
        return symbols['100']+symbols['500'];
    }
    if(num == 5){
        return symbols['500'];
    }
    if(num == 6){
        return symbols['500']+symbols['100'];
    }
    if(num > 5 && num < 9){
        return symbols['500'] + (symbols['100'].repeat(num%5));
    }
    if(num == 9){
        return symbols['100']+ symbols['1000']
    }
}

function convert4DigitNum(num){  
    return symbols['1000'].repeat(num);
}