Criticize my solution [Roman Numeral Converter]

I solved this but, my code seems so big and many repetitions.
My previous code was smaller but having issues in 5 test cases.
Here is the problem, Roman Numeral Converter.
Here is my code below -

function convertToRoman(num) {
    let result = [];
    let final = [];
    let str = String(num);

    //this loop is for beaking number to their positional value
    for(let i=0; i<str.length; i++){
        result.push(parseInt(str[i])*parseInt('1'+'0'.repeat((str.length-1)-i)));
    }
    //this function is for - number>= 1000
    function thousands(x){
        for(let i=0; i<x/1000; i++){
            final.push("M");
        }
    }
    //this function is for - number>= 100
    function hundreds(x){
        let subFinal = [];
        if(x/100<4){
            for(let i=0; i<x/100; i++){
                subFinal.push('C');
            }
            final.push(subFinal.join(""));
        }else if(x/100 === 4){
            final.push('CD');
        }else if(x/100 === 5){
            final.push('D');
        }else if(x/100 === 6){
            final.push('DC');
        }else if(x/100 === 7){
            final.push('DCC');
        }else if(x/100 === 8){
            final.push('DCCC');
        }else if(x/100 === 9){
            final.push('CM');
        }
    }

    //this function is for - number>= 10
    function tens(x){
        let subFinal = [];
        if(x/10<4){
            for(let i=0; i<x/10; i++){
                subFinal.push('X');
            }
            final.push(subFinal.join(""));
        }else if(x/10 === 4){
            final.push('XL');
        }else if(x/10 === 5){
            final.push('L');
        }else if(x/10 === 6){
            final.push('LX');
        }else if(x/10 === 7){
            final.push('LXX');
        }else if(x/10 === 8){
            final.push('LXXX');
        }else if(x/10 === 9){
            final.push('XC');
        }
    }
    //this function is for - number< 10
    function units(x){
        let subFinal = [];
        if(x<4){
            for(let i=0; i<x; i++){
                subFinal.push('I');
            }
            final.push(subFinal.join(""));
        }else if(x === 4){
            final.push('IV');
        }else if(x === 5){
            final.push('V');
        }else if(x === 6){
            final.push('VI');
        }else if(x === 7){
            final.push('VII')
        }else if(x === 8){
            final.push('VIII')
        }else if(x === 9){
            final.push('IX');
        }
    }

    //this loop is to convert all positional value to roman numerals
    for(let i=0; i<str.length; i++){
        if(result[i]>=1000){
            thousands(result[i]);
        }else if(result[i]>=100){
            hundreds(result[i]);
        }else if(result[i]>=10){
            tens(result[i]);
        }else{
            units(result[i]);
        }
    }
 return final.join("");
}

Feel free to suggest me to make my code more smart :heart: