ES6: console.log on WeakSet给出<item unknown>

Question

为什么console.log将WeakSet显示为<items unknown>

[13:37:11] [~] node
Welcome to Node.js v14.4.0.
Type ".help" for more information.
> let student1 = { name: 'James', age: 26 };
undefined
> let student2 = { name: 'Julia', age: 27 };
undefined
> const roster = new WeakSet([student1, student2]);
undefined
> console.log(roster);
WeakSet { <items unknown> }
undefined

上下文:我在WeakSet的ES6中遇到了下面的例子。

let student1 = { name: 'James', age: 26 };
let student2 = { name: 'Julia', age: 27 };
const roster = new WeakSet([student1, student2]);
console.log(roster);

这个例子表明它应该打印

WeakSet {Object {name: 'Julia', age: 27}, Object {name: 'Richard', age: 31}}

但在节点v14.4.0中，它会打印

WeakSet { <items unknown> }

Answer 1

节点-js团队决定很难正确地实现这一点。下面是问题：https://github.com/nodejs/node/issues/19001

这意味着WeakSet工作正常，但是console.log总是输出一个空的WeakSet

如果还想检查WeakMap，可以使用utils检查：

const { inspect } = require('util');
let student1 = { name: 'James', age: 26 };
let student2 = { name: 'Julia', age: 27 };
const weakSet = new WeakSet([student1, student2]);
console.log(inspect(weakSet, { showHidden: true }));