Heroku 在 server.js 中找不到 express

Question

在将我的 react 应用程序部署到 Heroku 时遇到困难。我收到以下错误：

ReferenceError: express is not defined

这里是项目结构：

• 后端文件夹
• 前端文件夹
• package.json
• 过程文件

这是我的 Procfile

web: node backend/server.js

这是根目录下的 package.json

  "name": "zippora",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "start": "node backend/server.js",
    "heroku-postbuild": "cd frontend && npm install && npm run build"
  },
  "engines": {
    "node": "16.4.1",
    "npm": "7.18.1"
  },
  "dependencies": {
    "bcrypt": "^5.0.0",
    "body-parser": "^1.19.0",
    "colors": "^1.4.0",
    "cors": "^2.8.5",
    "dotenv": "^8.2.0",
    "express": "^5.0.0-alpha.8",
    "jsonschema": "^1.4.0",
    "jsonwebtoken": "^8.5.1",
    "morgan": "^1.10.0",
    "pg": "^8.3.0"
  }
}

后端文件夹中的我的 server.js 文件

const app = require("./app.js");
const { PORT } = require("./config");
app.use(express.static("../frontend/build/index.html"))
app.get("/", (res,req) => {
  res.send({"message":"Hello?"})
})
app.listen(PORT, function () {
  console.log(`Started on http://localhost:${PORT}`);
});

我的 app.js 文件在后端的顶部

/** Express app for zippora. */

const express = require("express");
const cors = require("cors");

const { NotFoundError } = require("./expressError");

const { authenticateJWT } = require("./middleware/auth");
const authRoutes = require("./routes/auth");
const usersRoutes = require("./routes/users");

const morgan = require("morgan");

const app = express();```

Answer 1

请在 server.js 中定义 express

const express = require('express');

您的 Server.js 代码变为 ...

const express = require('express');
const app = require("./app.js");
const { PORT } = require("./config");
app.use(express.static("../frontend/build/index.html"))
app.get("/", (res,req) => {
  res.send({"message":"Hello?"})
})
app.listen(PORT, function () {
  console.log(`Started on http://localhost:${PORT}`);
});