删除对象时的 JavaScript 奇怪行为

Question

我做了以下事情:

a = {a:1};
b = {b:1};

c = [a,b]

delete a;

现在我不明白为什么 c 仍然有两个对象:[a, b] 但是当我尝试打印时，控制台给我: 未捕获的 ReferenceError:a 未定义

对象似乎不存在了，但它仍然存在于数组中。

我也试过打印:

typeof a //"undefined"

typeof c[0] //"object"

我确信当将一个对象分配给一个变量时，它是通过引用分配的。好像这里的对象被复制了？

Answer 1

Unlike what common belief suggests, the delete operator has nothing to do with directly freeing memory. Memory management is done indirectly via breaking references, see the memory management page for more details.

阅读here

即使在您删除 a 之后，a 的引用仍将存储在 c 中。

因此 c 将始终是 object 类型。

a = {a:1};
b = {b:1};

c = [a,b];

delete a;

console.log(c);

上面的代码会返回:

[
  {
    "a": 1
  },
  {
    "b": 1
  }
]

但是如果你删除 delete c[0].a 那么它会从数组 c 中删除 a :

a = {a:1};
b = {b:1};
c = [a,b];
console.log (delete c[0].a);
console.log(c);

输出将是:

[
  {},
  {
    "b": 1
  }
]