Js recursive factorial analysis

function  demo(num){
  if(num<=1){
    return 1;
  }
  return num*demo(num-1);
}

alert(demo(5))    //stdout:120


Execute the process：

1.return 5*demo(4)
2.return 4*demo(3)
3.return 3*demo(2)
4.return 2*demo(1)
5.if(num<=1) == true   return 1
6.return 1*1  return 1
7.return 2*1  return 2
8.return 3*2  return 6
9.return 4*6  return 24
10.return 5*24 return 120