Mastering Nodemon: Change Nodemon script depending on the changed file(s)

In the world of Node.js development, Nodemon is a go-to tool for automatically restarting your application when changes are detected in your code. But did you know that you can take Nodemon to the next level by changing its script depending on the changed file(s)? In this article, we’ll dive into the world of Nodemon’s advanced features and show you how to customize its behavior to fit your specific needs.

Why change Nodemon’s script?

So, why would you want to change Nodemon’s script depending on the changed file(s)? Well, there are several scenarios where this feature comes in handy:

• Optimize performance: By only running specific scripts when certain files change, you can significantly reduce the overhead of unnecessary script re-runs.
• Streamline development: With customized scripts, you can automate tasks specific to certain files or folders, making your development workflow more efficient.
• Enhance security: By restricting script execution to specific files or folders, you can prevent potential security threats and reduce the attack surface.

Understanding Nodemon’s configuration

To change Nodemon’s script depending on the changed file(s), you need to understand how Nodemon’s configuration works. Nodemon uses a configuration file called nodemon.json (or nodemon.config.js if you prefer a JavaScript file) to store its settings.

// nodemon.json
{
  "script": {
    "start": "node app.js"
  },
  "watch": ["src/**/*"],
  "ext": "js json"
}

In the above example, Nodemon is configured to watch for changes in the src folder and its subfolders, and restart the application when changes are detected. The script.start property specifies the script to run when Nodemon starts.

Using the `events` property

To change Nodemon’s script depending on the changed file(s), you need to utilize the events property in your configuration file. The events property is an object that allows you to define custom events that trigger specific scripts.

// nodemon.json
{
  "script": {
    "start": "node app.js"
  },
  "watch": ["src/**/*"],
  "ext": "js json",
  "events": {
    "change": {
      "src/controllers/*.js": "node ./src/controllers/*",
      "src/models/*.js": "sequelize db:migrate"
    }
  }
}

In this example, we’ve added an events(change) property that specifies two conditions:

• When a file in the src/controllers folder changes, Nodemon will run the script specified in the node ./src/controllers/* command.
• When a file in the src/models folder changes, Nodemon will run the script specified in the sequelize db:migrate command.

Using the `restartable` property

In addition to the events property, you can also use the restartable property to specify which files or folders should trigger a script re-run. The restartable property is a Boolean value that indicates whether Nodemon should restart the script when changes are detected.

// nodemon.json
{
  "script": {
    "start": "node app.js"
  },
  "watch": ["src/**/*"],
  "ext": "js json",
  "restartable": {
    "src/controllers/*.js": true,
    "src/models/*.js": false
  }
}

In this example, Nodemon will only restart the script when changes are detected in the src/controllers folder, but not when changes are detected in the src/models folder.

Using environment variables

You can also use environment variables to customize Nodemon’s behavior. For example, you can set an environment variable to specify the script to run depending on the changed file(s).

// nodemon.json
{
  "script": {
    "start": "node app.js"
  },
  "watch": ["src/**/*"],
  "ext": "js json",
  "env": {
    "NODE_ENV": "development"
  },
  "events": {
    "change": {
      "src/controllers/*.js": "NODE_ENV=staging node ./src/controllers/*",
      "src/models/*.js": "NODE_ENV=production sequelize db:migrate"
    }
  }
}

In this example, we’ve set an environment variable called NODE_ENV to development by default. However, when changes are detected in the src/controllers folder, Nodemon will set NODE_ENV to staging and run the script specified in the node ./src/controllers/* command. Similarly, when changes are detected in the src/models folder, Nodemon will set NODE_ENV to production and run the script specified in the sequelize db:migrate command.

Best practices and tips

When changing Nodemon’s script depending on the changed file(s), keep the following best practices and tips in mind:

• Keep it simple: Avoid over-complicating your configuration file by keeping your scripts and events concise and focused on specific tasks.
• Use meaningful names: Use descriptive names for your scripts and events to make it easy to understand what each one does.
• Test thoroughly: Thoroughly test your configuration file to ensure that it works as expected under different scenarios.
• Document your configuration: Document your configuration file and the logic behind it to make it easy for others (or your future self) to understand.

Conclusion

In conclusion, changing Nodemon’s script depending on the changed file(s) is a powerful feature that can greatly enhance your development workflow. By utilizing the events property, restartable property, and environment variables, you can create customized scripts that fit your specific needs. Remember to keep it simple, use meaningful names, test thoroughly, and document your configuration to get the most out of this feature.

Property	Description
events	Specifies custom events that trigger specific scripts.
restartable	Indicates whether Nodemon should restart the script when changes are detected.
env	Specifies environment variables that can be used in scripts.

By mastering this feature, you’ll be able to take your Node.js development to the next level and create a more efficient, streamlined, and secure development workflow. Happy coding!

Frequently Asked Question

Are you tired of nodemon constantly reloading your server whenever you make a change to your code? Want to know how to customize nodemon to refresh only when specific files are modified? Look no further!