Solution to problem presented at https://dev.to/albinotonnina/how-to-lose-a-it-job-in-10-minutes-35pi

cities.js

const cities = ['Tokyo', 'London', 'Rome', 'Donlon', 'Kyoto', 'Paris']

// Initially I misunderstood the problem and assumed that the letters
// could be reconfigured in any order to be a match
function sameLetters(city1, city2) {
  if (city1.length !== city2.length) return false
  for (let i = 0; i < city1.length; ++i) {
    if (!city2.includes(city1[i])) return false
    city2 = city2.replace(city1[i], '')
  }

  return city2.length === 0
}

// But as I continued to read the blog post I learned that it
// is just a rotation instead
function isRotated(city1, city2) {
  if (city1.length !== city2.length) return false
  let rotated = city2
  for (let i = 0; i < city2.length; ++i) {
    if (city1 === rotated) return true
    rotated = rotated.slice(1) + rotated[0]
  } 
  return false
}

const matches = []
let remaining = cities
while (remaining.length > 0) {
  matches[matches.length] = []
  const currentCity = remaining[0].toLowerCase()

  remaining.forEach(city => {
    if (isRotated(currentCity, city.toLowerCase())) matches[matches.length-1].push(city)
  })
  remaining = remaining.filter(city => !matches[matches.length-1].includes(city))
}

console.log(matches)