development environment - How to watch and reload ts-node when TypeScript files change

Development environment - How to watch and reload ts-node when TypeScript files change

To watch and reload TypeScript files automatically when they change, especially when using ts-node to run TypeScript files directly, you can utilize a tool like nodemon. nodemon monitors changes in your source code files and automatically restarts the application when changes are detected. Here's how you can set it up:

  1. Install nodemon and ts-node: First, make sure you have nodemon and ts-node installed globally or locally in your project.

    npm install -g nodemon ts-node

  2. Run your TypeScript files with ts-node and nodemon: Instead of running ts-node directly, you will run it through nodemon. For example:

    nodemon --exec ts-node your_file.ts

  3. Configure nodemon (optional): You can create a nodemon.json file in the root of your project to configure nodemon. For example:

    { "watch": ["src"], "ext": "ts", "exec": "ts-node ./src/your_file.ts" }

    This configuration tells nodemon to watch the src directory for changes with the .ts extension and execute ts-node on the specified file.

  4. Run nodemon: Simply run nodemon in your terminal, passing the TypeScript file you want to execute:

    nodemon your_file.ts

Now, whenever you make changes to your TypeScript files, nodemon will automatically detect the changes, recompile them with ts-node, and restart your application, providing a seamless development experience.

Examples

  1. Using ts-node-dev to Watch and Reload TypeScript Files

    • Description: This snippet demonstrates how to use ts-node-dev to watch for changes in TypeScript files and automatically reload the application.
    • Code:
      # Install ts-node-dev globally or as a development dependency npm install ts-node-dev --save-dev # Start your application with ts-node-dev to watch and reload on changes npx ts-node-dev index.ts

  2. Using nodemon to Watch and Reload TypeScript Files

    • Description: This query shows how to use nodemon with ts-node to watch for changes in TypeScript files and reload the application.
    • Code:
      # Install nodemon and ts-node npm install nodemon ts-node --save-dev # Create a nodemon.json configuration file echo '{ "watch": ["src/"], "ext": "ts", "exec": "ts-node src/index.ts" }' > nodemon.json # Start your application with nodemon to watch and reload on changes npx nodemon

  3. Watching TypeScript Files in a Specific Directory

    • Description: This snippet demonstrates how to watch TypeScript files in a specific directory and reload on changes.
    • Code:
      # Using ts-node-dev to watch a specific directory npx ts-node-dev --watch src/ src/index.ts # Or with nodemon to watch a specific directory npx nodemon --watch src/ --ext ts --exec "ts-node src/index.ts"

  4. Using npm run with a Watch Script for TypeScript

    • Description: This code snippet shows how to create an npm script that uses ts-node-dev or nodemon to watch and reload on TypeScript file changes.
    • Code:
      { "scripts": { "dev": "ts-node-dev --watch src/ src/index.ts" } } # Run the development script to watch and reload on changes npm run dev

  5. Configuring ts-node-dev to Watch Additional File Extensions

    • Description: This query shows how to configure ts-node-dev to watch for changes in additional file extensions, such as .json or .yaml.
    • Code:
      # Using ts-node-dev to watch additional extensions npx ts-node-dev --watch src/ --ext ts,json src/index.ts

  6. Handling Errors When Watching and Reloading TypeScript Files

    • Description: This snippet demonstrates how to handle errors when using ts-node-dev or nodemon to watch and reload TypeScript files.
    • Code:
      # Start ts-node-dev with error handling npx ts-node-dev --respawn src/index.ts # Or with nodemon to handle errors npx nodemon --delay 1 --exec "ts-node src/index.ts"

  7. Watching and Reloading with Custom tsconfig.json

    • Description: This snippet shows how to watch and reload TypeScript files with a custom TypeScript configuration.
    • Code:
      # Create a custom tsconfig.json file echo '{ "compilerOptions": { "target": "ES6", "module": "commonjs", "strict": true } }' > tsconfig.json # Start ts-node-dev with the custom tsconfig.json npx ts-node-dev --project tsconfig.json src/index.ts

  8. Using --inspect with ts-node-dev for Debugging

    • Description: This query demonstrates how to use the --inspect option with ts-node-dev to enable debugging while watching TypeScript files.
    • Code:
      # Start ts-node-dev with debugging enabled npx ts-node-dev --inspect --watch src/ src/index.ts # Or with nodemon to enable debugging npx nodemon --inspect --exec "ts-node src/index.ts"

  9. Watching and Reloading with Custom Environment Variables

    • Description: This snippet shows how to use custom environment variables when watching and reloading TypeScript files.
    • Code:
      # Set an environment variable and run ts-node-dev MY_VAR=123 npx ts-node-dev --watch src/ src/index.ts # Or with nodemon to use environment variables MY_VAR=123 npx nodemon --watch src/ --exec "ts-node src/index.ts"

  10. Using ts-node-dev with nodemon for Flexible Watching and Reloading

    • Description: This snippet demonstrates how to combine ts-node-dev and nodemon for flexible watching and reloading of TypeScript files.
    • Code:
      # Create a nodemon.json configuration for flexible watching echo '{ "watch": ["src/"], "ext": "ts", "exec": "ts-node-dev src/index.ts" }' > nodemon.json # Start with nodemon using the configuration npx nodemon

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