areumH.js

function getGenresCount(genres, plays) {
  const genresCount = {};

  genres.forEach((el, idx) => {
    genresCount[el] = (genresCount[el] || 0) + plays[idx][0];
  });

  return Object.entries(genresCount)
    .sort((a, b) => b[1] - a[1])
    .map((el) => el[0]);
}

function solution(genres, plays) {
  let answer = [];

  const indexPlays = plays.map((el, idx) => [el, idx]);
  const sortGenres = getGenresCount(genres, indexPlays);

  const genresIndex = sortGenres.map((el) => {
    return genres.map((genre, idx) => (el === genre ? idx : -1)).filter((idx) => idx !== -1);
  });

  for (let i = 0; i < genresIndex.length; i++) {
    const selected = genresIndex[i].map((idx) => indexPlays[idx]);
    answer.push(
      selected
        .sort((a, b) => b[0] - a[0])
        .slice(0, 2)
        .map((el) => el[1])
    );
  }

  return answer.flat();
}