我正在尝试使用node.js，react和MongoDB将我的应用程序部署到Heroku；部署成功；但是，该网站无法从MongoDB获取数据。 错误是GET http://localhost:5000/comment net::ERR_CONNECTION_REFUSED和Uncaught (in promise) Error: Network Error，我认为这是因为后端没有运行node server.js。谁能帮助我正确部署此方法？ 我在后端的pakage.json是

    "client-install": "npm install --prefix myprofile","start":"node server.js","server":"nodemon server.js","client":"npm start --prefix myprofile","dev":"concurrently \"npm run server\" \"npm run client\"","heroku-postbuild":"NPM_CONFIG_PRODUCTION=false npm install --prefix myprofile && npm run build --prefix myprofile"
  }

我的server.js是

const express = require("express");
const cors = require("cors");
const mongoose = require("mongoose");
const path = require("path");
require("dotenv").config();

const app = express();
const port = process.env.PORT || 5000;

app.use(express.json());
app.use(cors());
//app.use(express.static(path.join(__dirname,'./myprofile/build')));

const uri = process.env.ATLAS_URI;
mongoose.connect(uri,{
  useNewUrlParser: true,useCreateIndex: true,useUnifiedTopology: true
});
const connection = mongoose.connection;
connection.once("open",() => {
  console.log("MongoDB data connected");
});
const CommentRouter = require("./CommentRouter");
app.use("/comment",CommentRouter);

if (process.env.NODE_ENV === "production") {
  app.use(express.static("myprofile/build"));
  app.get("*",(req,res) => {
    res.sendFile(path.resolve(__dirname,"myprofile","build","index.html"));
  });
}

app.listen(port,() => console.log(`Server is running on ${port}`));

非常感谢您！