for문 - 연속되는 문자열

let answer = '';
let base = str[0];
let count = 1;

str = str + ' ';

for(let i = 1; i<str.length; i++){
    if(base === str[i]){
      count++;
    }else{
      answer += (count >= 3) ? `${count}${base}` : base.repeat(count);

      base = str[i];
      count = 1;
    }
}

return answer;