1 false
   2 true
   3 true
   4 true
   5 false
   6 false
   7 false
   8 true
   9 side effect
  10 true
  11 number
  12 w 10
  13 function
  14 false
  15 10
  16 false
  17 10
  18 false
  19 33
  20 false
  21 20
  22 20
  23 true
  24 20
  25 undefined