How to Watch and Reload ts-node When TypeScript Files Change

Solution 1 : Using Nodemon with ts-node

Step 1: Install Required Packages

npm install ts-node nodemon typescript --save-dev

Step 2: Create a nodemon.json Configuration File

Add a nodemon.json file to your project root with the following content:

{
  "watch": ["src"],  // Directory or files to watch
  "ext": "ts",       // File extensions to watch
  "ignore": ["dist"], // Directories to ignore
  "exec": "ts-node ./src/index.ts" // Command to execute
}

Step 3: Run nodemon

Use nodemon to start your application:

npx nodemon
Or
"scripts": {
  "start": "npx nodemon"
}

Alternative if we dont want to create a nodemon.json file then we can execute following command directly or we can add it to package. Json.

npx nodemon --watch src --ext ts --exec "ts-node ./src/index.ts"

Pros:-

1. Mature and Flexible:
   • nodemon offers a wide range of configuration options, such as ignoring files, specifying extensions, and handling custom scripts.
   • You can fine-tune what to watch or ignore, making it suitable for larger projects.
2. Compatible with Complex Workflows:
   • Works well with tools like preprocessors or additional build steps.
   • Can integrate with custom tasks (e.g., linting or running multiple commands).
3. Community Support:
   • Widely used, so you’ll find plenty of resources, plugins, and fixes for common problems.

Cons:-

1. Dependency Overhead:
   • Requires installing nodemon and configuring it, which adds extra setup and dependencies.
2. Performance:
   • Slightly slower for very large projects since it monitors a broader range of files.

Solution 2 : Using Node.js’s Built-in –watch Mode

We can use Node.js’s built-in –watch mode which monitors files for changes and restarts your application automatically. This feature is available from Node.js v18.11.0 and later.
We can use this command to run ts-node directly using node js built in watch mode.

node --watch -r ts-node/register ./src/index.ts

Pros:-

• Lightweight:

• No need to install additional tools like nodemon. Ideal for smaller projects or minimal setups.

• Built-In Simplicity:
  • Reduces dependency management.

• • The –watch mode is easy to enable with no extra configuration.

• Good for Small-to-Medium Projects:

1. • Works well for straightforward applications without a lot of custom requirements.

Cons:-

• Less Configurable:

• You can’t exclude specific file types or directories unless you set environment variables (NODE_WATCH_IGNORE).
  • No support for additional workflows like running custom scripts.

• Not Feature-Rich:

1. • Limited to restarting the application when files change. It lacks advanced capabilities like conditional restart logic or task runners.

Recommendation

1. Use nodemon with ts-node if:
   • You need advanced features like ignoring specific files or directories.
   • You work on large or complex projects with custom workflows.
   • You prefer a mature and well-supported solution.
2. Use Node.js Watch Mode if:
   • You prefer simplicity and fewer dependencies.
   • You’re working on a smaller project or want a lightweight setup.
   • You’re exploring Node.js’s built-in capabilities for a minimalist approach.