1 x instanceof f: true
   2 x instanceof b: true
   3 y instanceof f: true
   4 y instanceof b: true
   5 
   6 Changing prototype
   7 
   8 x instanceof f: false
   9 x instanceof b: false
  10 y instanceof f: false
  11 y instanceof b: false
  12 Bound function prototype
  13 
  14 f.hasOwnProperty('prototype'): true
  15 b.hasOwnProperty('prototype'): false