[プログラマー]新しいアイデンティティを推奨

function solution(new_id) {
    var answer = '';
    answer = new_id.toLowerCase();
    
    answer = answer.replace(/[^a-z0-9-_.]/gi,"");
    answer = answer.replace(/\.+/g, '.'); //하나 이상이면 .으로 치환
    
    if(answer[0]==='.')
        answer = answer.slice(1);
    if(answer[answer.length-1]==='.')
        answer = answer.slice(0, answer.length-1);
    if(answer.length==0)
        answer = "a";
    if(answer.length>15){
        answer = answer.slice(0,15);
        if(answer[answer.length-1]==='.'){
            answer = answer.slice(0, answer.length-1);}
    }
    if(answer.length<=2)
    {
        var tmp = answer[answer.length-1];
        while(answer.length<3)
        {
            answer += tmp;
        }
    }
    console.log(answer);
    
    return answer;
}