WeakMap

Question

  const weakm = new WeakMap();

  let keyObject = {id : 1};

  const valObject = {score : 100};

  weakm.set(keyObject,valObject);

  console.log(weakm.get(keyObject));

  keyObject = null;

  console.log(weakm);

  console.log(weakm.get(keyObject));

打印结果：

为什么打印weakm还有键 {id：1}，各位赐教

Answer 1

额，可能是浏览器为了让你方便查看里面的值吧，所以一直记录了下来，不过在 node 中是不会打印任何值的