프로그래머스 | 베스트 앨범

function solution(genres, plays) {
    var answer = [];
    let obj=genres.reduce((acc,e,idx)=>{
       if(e in acc) {
           acc[e].plays+=plays[idx]
       }else{
           acc[e]={
               plays:plays[idx],
               music:[]
           }
       }
        acc[e].music.push([idx,plays[idx]])
        return acc;
    },{});
    let sorted=Object.values(obj).sort((a,b)=>b.plays-a.plays);
    sorted.forEach(e=>{
        if(e.music.length>1){
            e.music.sort((a,b)=>b[1]-a[1]);
            answer.push(e.music[0][0]);
            answer.push(e.music[1][0]);
        }else{
            answer.push(e.music[0][0])
        }
        
        
    })
    return answer;
}