code: function equalArrayElements (needle, haystack) {
    let missingNeedle = needle.filter(n => haystack.indexOf(n) === -1)
    if (missingNeedle.length !== 0) {
      return false
    }
  
    let missingHaystack = haystack.filter(h => needle.indexOf(h) === -1)
    return missingHaystack.length === 0
  }
docs: See if two arrays contain the same elements