TypeError:无法读取未定义的属性(读取“config”)

Question

这是我的app.ts文件：

import express, { Request, Response } from "express";
import dotenv from "dotenv";
dotenv.config();
import config from "config";
import responseTime from "response-time";
import connect from "./utils/connect";
import logger from "./utils/logger";
import routes from "./routes";
import deserializeUser from "./middleware/deserializeUser";
import { restResponseTimeHistogram, startMetricsServer } from "./utils/metrics";
import swaggerDocs from "./utils/swagger";

const port = config.get<number>("port");

const app = express();

app.use(express.json());

app.use(deserializeUser);

app.use(
  responseTime((req: Request, res: Response, time: number) => {
    if (req?.route?.path) {
      restResponseTimeHistogram.observe(
        {
          method: req.method,
          route: req.route.path,
          status_code: res.statusCode,
        },
        time * 1000
      );
    }
  })
);

app.listen(port, async () => {
  logger.info(`App is running at http://localhost:${port}`);

  await connect();

  routes(app);

  startMetricsServer();

  swaggerDocs(app, port);
});

我确实收到了这样的错误信息：

yarn dev
yarn run v1.22.17
warning package.json: License should be a valid SPDX license expression
warning ..\..\..\..\package.json: No license field
$ ts-node-dev --respawn --transpile-only src/app.ts
[INFO] 14:02:52 ts-node-dev ver. 1.1.8 (using ts-node ver. 9.1.1, typescript ver. 4.6.3)
TypeError: Cannot read properties of undefined (reading 'config')
    at Object.<anonymous> (C:\Users\A\Desktop\desktop\base_code\back_bc_node\src\app.ts:3:8)
    at Module._compile (node:internal/modules/cjs/loader:1103:14)
    at Module._compile (C:\Users\A\Desktop\desktop\base_code\back_bc_node\node_modules\source-map-support\source-map-support.js:568:25)
    at Module.m._compile (C:\Users\A\AppData\Local\Temp\ts-node-dev-hook-16796532812275466.js:69:33)
    at Module._extensions..js (node:internal/modules/cjs/loader:1155:10)
    at require.extensions.<computed> (C:\Users\A\AppData\Local\Temp\ts-node-dev-hook-16796532812275466.js:71:20)
    at Object.nodeDevHook [as .ts] (C:\Users\A\Desktop\desktop\base_code\back_bc_node\node_modules\ts-node-dev\lib\hook.js:63:13)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
[ERROR] 14:02:52 TypeError: Cannot read properties of undefined (reading 'config')

为什么我会收到这条错误消息？我已经用dotenv version 10处理了之前的应用程序，但是当我用dotenv version 16在我的新应用程序中复制它时，我得到了一条错误消息。

这是我的package.json文件：

{
  "name": "back_bc_node",
  "version": "1.0.0",
  "main": "index.js",
  "license": "Commercial",
  "scripts": {
    "dev": "ts-node-dev --respawn --transpile-only src/app.ts",
    "build": "tsc"
  },
  "dependencies": {
    "bcrypt": "^5.0.1",
    "config": "^3.3.7",
    "cors": "^2.8.5",
    "dayjs": "^1.11.0",
    "dotenv": "^16.0.0",
    "express": "^4.17.3",
    "jsonwebtoken": "^8.5.1",
    "lodash": "^4.17.21",
    "mongoose": "^6.2.10",
    "nanoid": "^3.3.2",
    "pino": "^7.10.0",
    "pino-pretty": "^7.6.1",
    "prom-client": "^14.0.1",
    "response-time": "^2.3.2",
    "swagger-jsdoc": "^6.2.0",
    "swagger-ui-express": "^4.3.0",
    "zod": "^3.14.4"
  },
  "devDependencies": {
    "@types/bcrypt": "^5.0.0",
    "@types/body-parser": "^1.19.2",
    "@types/config": "^0.0.41",
    "@types/cors": "^2.8.12",
    "@types/express": "^4.17.13",
    "@types/jsonwebtoken": "^8.5.8",
    "@types/lodash": "^4.14.181",
    "@types/nanoid": "^3.0.0",
    "@types/node": "^17.0.23",
    "@types/pino": "^7.0.5",
    "@types/response-time": "^2.3.5",
    "ts-node-dev": "^1.1.8",
    "typescript": "^4.6.3"
  }
}

Answer 1

试着替换：

import dotenv from "dotenv";

为此：

import * as dotenv from 'dotenv'

Answer 2

我也遇到了这个问题，我解决了这个问题：

创建一个新项目，移动旧项目中的重要文件(对我来说，Vue项目中的所有src文件)，然后启动项目，成功！

Answer 3

这是因为您试图在es模块中使用commonJS语法。dotenv.config函数用于commonJS，并使用TypeScript ES模块。为了更好地使用，请看一下dotenv的文档：

dotenv文档