不能在会话变量 express 中使用 "Set"

Question

我试图将 Set 用作会话值，但由于某种原因，我得到了这个意外的结果。我正在从客户端向这条路线发出两个请求。

app.post("/api/add_to_cart", (req, res) => {
    console.log(req.session.productList);
    if (req.session.productList === undefined)
        req.session.productList = new Set();
    console.log(req.session.productList);
    req.session.productList.add('one');
    console.log(req.session.productList);
    res.send();
});

输出：

undefined
Set(0) {}
Set(1) { 'one' }

{}
{}
TypeError: req.session.productList.add is not a function

但是如果我使用数组而不是 Set，它会按预期工作

app.post("/api/add_to_cart", (req, res) => {
    console.log(req.session.productList);
    if (req.session.productList === undefined)
        req.session.productList = [];
    console.log(req.session.productList);
    req.session.productList.push('one');
    console.log(req.session.productList);
    res.send();
});

输出：

undefined
[]
[ 'one' ]

[ 'one' ]
[ 'one' ]
[ 'one', 'one' ]

由于某些未知原因，Set 对象正在更改为 {}。

Answer 1

来自the docs：

req.session

To store or access session data, simply use the request property req.session, which is (generally) serialized as JSON by the store, so nested objects are typically fine.
_{(highlighting mine)}

…和 / 开箱即用。

内置开发专用 MemoryStore does this。

不能在会话变量 express 中使用 "Set"

cannot use "Set" in a session variable express

javascript

node.js

express

express-session

`req.session`