1 obj1.valueOf 2 obj1 is 1 3 obj1.valueOf 4 11 5 obj2.valueOf 6 obj2 is 2 7 obj2.valueOf 8 24 9 obj1.valueOf 10 obj2.valueOf 11 3 12 obj3.toString 13 world12 14 obj3.toString 15 hello world 16 obj1.valueOf 17 obj3.toString 18 1world 19 obj2.valueOf 20 obj3.toString 21 2world 22 obj3.toString 23 obj3.toString 24 worldworld