有效避免JS全局变量污染

var A = {};//必须定义为对象

A.person = {
    name:"zhangsan",
    age:18,
    body:{
        height:"180cm",
        weight:"70kg"
    }
};
//var 定义的全局不能被删除
// delete A;
//隐式全局变量被删除
// delete A.person;
console.log(A);
console.log(A.person);
console.log(A.person.name);
console.log(A.person.body.height);
// alert(JSON.stringify(A.person))

(function(){
    var a="abc";
    console.log("a:"+a);
    console.log(A.person.age);
})()
// alert(a)