function quickSort(array)
{
  if(array.length<=1){
    return array
  }
  let flagNumber = array[0],left = [],right = []  
  for(let i =1;i<array.length;i++){
    if(array[i]-flagNumber<=0){
      left.push(array[i])
    }else{
       right.push(array[i])
    }
  }
  if(left.length<=1&&right.length<=1){
    return left.concat([flagNumber]).concat(right)
  }
  return quickSort(left).concat([flagNumber]).concat(quickSort(right))
}

console.log(quickSort([2,7,90,3,1,89,9,20,0]))