Unknown file extension “.ts” for /app/src/index.ts starting node app in combination with nodemon

Unknown file extension “.ts” for /app/src/index.ts starting node app in combination with nodemon

If you are encountering the error message “Unknown file extension ‘.ts’ for /app/src/index.ts starting node app” when trying to start your Node.js app using nodemon, don’t worry, you’re not alone. This error typically occurs when nodemon is unable to recognize TypeScript files with the “.ts” extension. In this blog post, we will explore a couple of solutions to fix this issue and get your app up and running smoothly.

Solution 1: Configure nodemon to recognize TypeScript files

The first solution involves configuring nodemon to recognize TypeScript files by adding a nodemon.json configuration file to your project’s root directory. This file allows you to specify custom settings for nodemon.

Create a new file named nodemon.json in your project’s root directory and add the following content:

{
    "ext": "ts",
    "exec": "ts-node ./app/src/index.ts"
  }

In the above configuration, we set the ext property to “ts” to tell nodemon to watch for changes in TypeScript files. Additionally, we specify the exec property to run the TypeScript file using ts-node.

Save the nodemon.json file and try running your app again with nodemon. The error should no longer occur, and nodemon should be able to recognize and execute your TypeScript files.

Solution 2: Use ts-node-dev instead of nodemon

If the first solution didn’t work for you or you prefer an alternative approach, you can use ts-node-dev instead of nodemon. ts-node-dev is a TypeScript execution and reloading tool specifically designed for development environments.

To use ts-node-dev, first, install it as a development dependency by running the following command:

npm install ts-node-dev --save-dev

Once installed, you can update your package.json file’s scripts section to use ts-node-dev instead of nodemon. Modify the start script as follows:

"scripts": {
    "start": "ts-node-dev ./app/src/index.ts"
  }

Save the package.json file and run your app using npm start. ts-node-dev will handle the TypeScript compilation and reloading of your app whenever changes are detected.

Conclusion

The “Unknown file extension ‘.ts’ for /app/src/index.ts starting node app” error can be resolved by either configuring nodemon to recognize TypeScript files or using ts-node-dev as an alternative. Choose the solution that works best for your project and get back to developing your TypeScript app without any interruptions.