将对象设置为 null 时的 JavaScript(ES6) WeakMap 垃圾收集 [英] JavaScript(ES6) WeakMap garbage collection when set an object to null
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收集，并且将对象分配给 null 等效于删除它:
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}
为什么输出一样?不是应该删除它以便 gc 可以重用之前在应用程序中占用的内存吗?我将不胜感激任何澄清.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
垃圾收集不会立即运行.如果你想让你的例子工作，你需要强制你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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