function myfun(a){
  a=a.split("")
  let count={}
  a.forEach((x)=>count[x]?count[x]++:count[x]=1)
  //count={ a: 2, b: 2, c: 1, d: 1, e: 2, s: 1 }
  let key=Object.keys(count)
  let val=Object.values(count)
  let result=""
  for(let i=0;i<key.length;i++){
    result+=val[i]+key[i]
  }
  return result
}
console.log(myfun("aabbcdees"))