permutations of base

function splitAllWays(result, left, right){
  result.push(left.concat(right));
  if (right.length > 1){
    for(var i = 1; i < right.length; i++){
      splitAllWays(result, left.concat(right.substring(0, i)), right.substring(i));
    }
  }

  return result;
};

function permutationsOfBase(str,sets) {
  let base = Array.from(new Set(str.split('')))
  let out = []
  base.forEach((x,i) => { 
    base.forEach((y,j) => {
      if (i === j) return
      let xCount = (str.match(new RegExp(x,'g')) || []).length
      let yCount = (str.match(new RegExp(y,'g')) || []).length
      sets.forEach(set => {
	      set.forEach(word => {
          let cxC = xCount
          let cyC = yCount
          let arranged = word.split('').map(l => {
            if(l === x && cyC) { 
              l = y
              cyC--
            } else if(l === y && cxC) {
              l = x
              cxC--
            }
            return l
          }).join('')
          out.push(arranged, word)
        })      
      })
    })
  })
  return Array.from(new Set(out))
}

var str = "3123";
permutationsOfBase(str,splitAllWays([], [], str)).sort()