I am trying to create and run a simple TypeScript NodeJS project. Followings are my codes:

server.ts:

import express from 'express';

const app = express();
const PORT = 3000;

app.listen(PORT , ()=>{
    console.log('Server is listening on port $PORT');
});

tsconfig.json:

{
  "compilerOptions": {
  
    "target": "esnext",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */

    "module": "commonjs",                                /* Specify what module code is generated. */
    "rootDir": "./src",                                  /* Specify the root folder within your source files. */
    "moduleResolution": "node",                       /* Specify how TypeScript looks up a file from a given module specifier. */

    "outDir": "./build",                                   /* Specify an output folder for all emitted files. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */

    "strict": true,                                      /* Enable all strict type-checking options. */
    "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
  }
}

package.json:

{
  "name": "back",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon build/server.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@types/express": "^4.17.13",
    "express": "^4.18.1",
    "mongoose": "^6.5.0",
    "nodemon": "^2.0.19"
  }
}

When I try npm start I get the following error message:

> [email protected] start       
> nodemon build/server.js

[nodemon] 2.0.19
[nodemon] to restart at any time, enter `rs`      
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json        
[nodemon] starting `node build/server.js index.js`
node:internal/modules/cjs/loader:936
  throw err;
  ^

Error: Cannot find module 'C:\Users\A\\Test\back\index.js'
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}
[nodemon] app crashed - waiting for file changes before starting...

CodePudding user response：

You've set your entry file to be index.js in package.json, so nodemon is trying to run both server.js and index.js, which does not exist. The simplest way you can solve this − provided that you've transpiled your TS files with tsc, for example − is to change the entry point main in package.json to build/server.js.

So what you have to do:

1. Install typescript to be able to transpile you code:

npm install typescript

2. Before running npm start, you have to make sure your code is transpiled, that is, "compiled" to vanilla JavaScript, so add this script to your package.json:

{
  "scripts": {
    // ...
    "build": "tsc"
  }
}

3. Update main in package.json to be build/server.js.
4. Run npm run build then finally npm start.

Done! Your server will start.

My tips before the answer update:

Also, creating a configuration file for nodemon (nodemon.json) will make things much simpler for you, take a look at the docs.

Lastly, if you're new at this, I recommend taking a look at some ready-made tsconfig bases from this repo, in special this one for Node 16.

CodePudding user response：

I modified my tsconfig.json file as following and it worked:

{
  "name": "back",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon src/server.ts"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@types/express": "^4.17.13",
    "express": "^4.18.1",
    "mongoose": "^6.5.0"
  },
  "devDependencies": {
    "nodemon": "^2.0.19",
    "ts-node-dev": "^2.0.0",
    "typescript": "^4.7.4"
  }
}

The created changes are in these lines:

"main": "index.js" To "main": "server.js"

"start": "nodemon build/server.js" To "start": "nodemon src/server.ts"