A function that takes an array of random words and outputs a two-dimensional array of anagrams.

anagram.js

// Very inefficient but purely declarative approach
const findAnagrams = words => {
  const pairIsAnagram = (word1, word2) =>
    word1.split('').sort()
      .reduce(
        (acc, el, i) => { acc[i] = el == acc[i]; return acc; },
        word2.split('').sort()
      )
      .reduce((acc, el, i) => acc && el, true);
  return words.map(
    word1 => words.reduce(
      (acc, word2, i) => word2 !== word1 && pairIsAnagram(word1, word2) ? [...acc, [word1, word2]] : [...acc], []
    )
  ).filter(el => el.length > 0)
   .map(el => el[0].sort())
   .reduce((acc, el) => acc.map(e => e.toString()).indexOf(el.toString()) < 0 ? [...acc, el] : [...acc], []);
};

const words = ['стол', 'барокко', 'слот', 'кот', 'кошка', 'ток', 'коробка'];
console.log(findAnagrams(words));
// [
//   ['стол', 'слот'],
//   ['кот', 'ток'],
//   ['барокко', 'коробка'],
// ]