javascript - 删除对象/关联数组

可以说我已经在JavaScript中创建了一个对象及其属性，如下所示:

   var obj = {};
   obj['bar'] = 123;
   obj['bar']['foo'] = new Array();
   obj['bar']['xyz'] = new Array();

之后，我将元素推入两个数组。
如果我再写

   delete obj['bar'];

两个数组也会被删除吗？

最佳答案

只要没有其他引用，它们将有资格进行垃圾回收。根据该代码，将不会有任何结果。何时以及是否真正清除它们取决于实现。

但是请注意，即使在删除bar之前，它们也有资格使用GC，因为您的代码做得很奇怪。查看评论:

// Creates a blank object, so far so good.
var obj = {};

// Sets the `bar` property to the number 123.
obj['bar'] = 123;

// Retrieves the value of `bar` (the primitive number 123) and
// *converts* it into a `Number` instance (object), then
// creates a property on that object called `foo`, assigning a
// blank array to it. Because the Number object is never stored
// anywhere, both it and the array are IMMEDIATELY eligible for
// garbage collection. The value of `obj['foo']` is unaffected,
// it remains a primitive number.
obj['bar']['foo'] = new Array();

// The same happens again, a temporary Number instance and
// array are created, but both are IMMEDIATELY eligible for
// garbage collection; the value of `obj['bar']` is unaffected.
obj['bar']['xyz'] = new Array();

因此，您甚至不必删除bar，这些数组即刻可以进行垃圾回收。发生这种情况是因为在JavaScript中，数字是可以自动提升为Number对象的基元-但不会影响分配给基元编号的属性的值。所以:

var obj = {};
obj['bar'] = 123;
obj['bar']['foo'] = [];         // [] is a better way to write new Array()
console.log(obj['bar']['foo']); // "undefined"

如果将obj['bar'] =行更改为:

obj['bar'] = {};

要么

obj['bar'] = []; // Arrays are objects

...然后foo和xyz属性不会立即消失，并且数组将一直存在，直到bar被清除为止。