javascript 对象属性引用

Question

谁能对这里发生的事情给出最好的解释:

var o = {
    name: "jack"
};

var z = {
    name: o.name
};

o = {};
alert(z.name); // expected undefined, shows "jack" instead

对象属性只是引用吗？销毁对象 o 似乎并没有销毁引用的对象(在本例中为字符串“jack”)。或者，o.name 引用的“jack”是否实际上已被销毁但 z.name 创建了 o.name 的副本？

最佳

// consider this too
var o = {
    foo: function () {
        return "hello";
    }
};

var z = {
    m: o.foo
};

o = {};
alert(z.m()); // hello is displayed

Answer 1

您可能会发现这更有趣。

var o = {
    name: "Jack"
};

var z = {
    name: o 
};

//Above assignment of 'o' to z.name will create a new alias to object 'o'. 
//So both 'o' and 'z.name' point to same object.

//When you change value inside 'o' it will still reflect in 'z.name' 
//because both point to same object
o.name="Jill";
console.log(z.name.name); // Logs : Jill and not Jack.

// Now, here you are actually assigning a new object to 'o'.
// This means now 'o' refers to a new object. But this will no way affect 
// the 'z.name' reference, it still points to same object. 
o = { name : "Joe"};
console.log(z.name.name); // Logs : Jill again and not Joe