Javascript 为什么fetch向heroku上的本地主机发送请求？

在server.js上，我有

const PORT = process.env.PORT || 5000;

我想这就是请求将端口设置为5000的原因，但是我如何修复它

我有一个express应用程序，服务于react前端，并向同一域名上的端点发出请求

它向我想要的某个url/auth发送请求，但同时也向localhost:5000/auth发送请求，这导致我的应用程序无法工作

即使package.json也没有将代理设置为本地主机端口，因此我无法理解为什么GET和POST请求同时指向localhost/auth和某个url/auth，而不仅仅指向某个url/auth

（客户端）app.js：

package.json：

{
  "name": "react-notes-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^4.2.4",
    "@testing-library/react": "^9.5.0",
    "@testing-library/user-event": "^7.2.1",
    "cors": "^2.8.5",
    "express-session": "^1.17.1",
    "md5": "^2.3.0",
    "mysql": "^2.18.1",
    "node-fetch": "^2.6.0",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-scripts": "3.4.3"
  },
  "scripts": {
    "start": "node api/server.js"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "engines":{
    "node":"v12.18.3",
    "npm":"6.14.6"
  }
}

---

我没有运行“npm run build”，所以它使用的是以前的版本，该版本的URL为localhost。

---

现在可以工作。

请告诉我们

URL

是在哪里定义的，以及如何定义的。在这个

const endpoint=URL+'/auth'

中

URL

和

endpoint

的值是多少？我建议在该语句之后添加一个

console.log（endpoint）

。@Bergi它是在类构造函数中定义的。另请参阅我编辑的文章。很好地显示了类构造函数。@guycongnitodone。检查编辑的帖子。

{
  "name": "react-notes-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^4.2.4",
    "@testing-library/react": "^9.5.0",
    "@testing-library/user-event": "^7.2.1",
    "cors": "^2.8.5",
    "express-session": "^1.17.1",
    "md5": "^2.3.0",
    "mysql": "^2.18.1",
    "node-fetch": "^2.6.0",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-scripts": "3.4.3"
  },
  "scripts": {
    "start": "node api/server.js"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "engines":{
    "node":"v12.18.3",
    "npm":"6.14.6"
  }
}