This may be because for cross-domain cookies you set {sameSite: true} and {secure: true}, but in your example you are doing it on http://localhost so it won't Set any cookies. Please refer to the link below for requirements.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite#samesitenone_requires_secure

Also set the correct headers, such as Access-Control-Allow-Credentials, Access-Control-Allow-Origin, Access-Control-Allow-Headers

You can use mkcert to refer to making a secure connection on localhost.

I also recommend using the same top-level domain on both frontend and backend, and using subdomains.

Another thing to note here is that if there is a port in the domain name, I don't think Chrome will set the cookie, please give it a try.

I successfully solved this problem so that others who come later can find the answer. I moved the declaration of cookieparser to just before where the sequelize connection is initialized. I also added the withCredentials option to my axios post request. With both steps, my cookies are now set correctly and accessible.

const express = require("express");
require("dotenv").config();
const cors = require("cors");
const app = express();
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
const cookieParser = require("cookie-parser");
app.use(cookieParser());
const port = process.env.PORT || 8080;
const lib = require("./lib"); //这是所有自定义函数
const sql = require("./database");

onSubmit() {
        let loginInfo = {
          email: email.value,
          password: password.value,
        };
        axios
          .post("http://localhost:3000/user/login", loginInfo, {
            withCredentials: true,
          })
          .then(() =>
            $q.notify({
              color: "green-4",
              textColor: "white",
              icon: "cloud_done",
              message: "帐户创建成功！",
            })
          )
          .catch(() =>
            $q.notify({
              color: "red-5",
              textColor: "white",
              icon: "warning",
              message: "电子邮件或用户名已被使用！",
            })
          );
      },