});
console.log("rn");
console.log("a has changed to 50,then the expr should has value 55");
data.a = 50;
console.log("rn");
console.log("b.c has changed to 50,then the expr should has value 122");
data.b.c = 72;;
console.log("rn");
console.log("b.c has reseted an object,then the expr should has value 80");
data.b = { c: 30 }
OK 大功告成
