将对象设置为 null 时的 JavaScript(ES6)WeakMap 垃圾回

问题描述

我刚刚读到 WeakMaps 通过专门使用对象作为键来利用垃圾回收，并且将对象分配给 null 相当于删除它:

I've just read that WeakMaps take advantage of garbage collection by working exclusively with objects as keys, and that assigning an object to null is equivalent to delete it:

let planet1 = {name: 'Coruscant', city: 'Galactic City'};
let planet2 = {name: 'Tatooine', city: 'Mos Eisley'};
let planet3 = {name: 'Kashyyyk', city: 'Rwookrrorro'};

const lore = new WeakMap();
lore.set(planet1, true);
lore.set(planet2, true);
lore.set(planet3, true);
console.log(lore); // output: WeakMap {{…} => true, {…} => true, {…} => true}

然后我将对象设置为null:

Then I set the object equal to null:

planet1 = null;
console.log(lore); // output: WeakMap {{…} => true, {…} => true, {…} => true}

为什么输出相同?难道不应该删除它，以便 gc 可以重用以前在应用程序中占用的内存吗?我将不胜感激.谢谢！

Why is the output the same? Wasn't it supposed to be deleted so that the gc could reuse the memory previously occupied later in the app? I would appreciate any clarification. Thanks!

推荐答案

垃圾回收没有立即运行.如果您希望您的示例正常工作，您需要强制您的浏览器运行垃圾收集.

Garbage collection does not run immediately. If you want your example to work you need to force your browser to run garbage collection.

使用以下标志运行 chrome:google-chrome --js-flags="--expose-gc".

Run chrome with the following flag: google-chrome --js-flags="--expose-gc".

您现在可以通过调用全局 gc() 方法来强制进行垃圾回收.

You can now force the garbage collection by calling the global gc() method.

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