ES6：WeakSet 上的 console.log 給出<item unknown></item>

Question

為什么console.log將 WeakSet 顯示為<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 ES6 中的WeakSet上遇到了以下示例。

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

該示例表明它應該打印

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

但在節點 v14.4.0 中，它會打印

WeakSet { <items unknown> }

Answer 1

node-js 團隊認為很難正確實現它。 這是問題： https://github.com/nodejs/node/issues/19001

所以這意味着 WeakSet 可以正常工作但 console.log 將始終 output 為空的 WeakSet

如果您仍想檢查 WeakMap，您可以使用 utils inspect 來做到這一點：

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 }));