Introduction to Chokidar: Efficient File Watching for Node.js

Chokidar is a highly efficient and powerful file watching library for Node.js that simplifies the process of monitoring file system changes. Its robust API enables developers to handle various file system events seamlessly. In this article, we’ll explore the key features and APIs Chokidar offers, along with practical examples to help you integrate this library into your applications effectively.

Getting Started with Chokidar

To use Chokidar in your project, first install it using npm:

  npm install chokidar

Basic Usage

Here’s a simple example of using Chokidar to watch for changes in a directory:

  const chokidar = require('chokidar');

  // Initialize watcher
  const watcher = chokidar.watch('./dir-to-watch', {
    ignored: /^\./,
    persistent: true
  });

  // Add event listeners
  watcher
    .on('add', path => console.log(`File ${path} has been added`))
    .on('change', path => console.log(`File ${path} has been changed`))
    .on('unlink', path => console.log(`File ${path} has been removed`));

Advanced API Usage

Watching Specific Files and Directories

Chokidar allows you to target specific files and directories:

  const watcher = chokidar.watch(['file1.txt', 'dir2'], {
    persistent: true
  });

Handling Events

Chokidar provides several event listeners to handle file system events:

  watcher
    .on('addDir', path => console.log(`Directory ${path} has been added`))
    .on('unlinkDir', path => console.log(`Directory ${path} has been removed`))
    .on('error', error => console.log(`Watcher error: ${error}`))
    .on('ready', () => console.log('Initial scan complete. Ready for changes'))
    .on('raw', (event, path, details) => {
      console.log('Raw event info:', event, path, details);
    });

Stopping the Watcher

To stop watching, you can use the close method:

  watcher.close().then(() => console.log('Watcher stopped'));

Practical Application Example

Let’s create a simple application that monitors a directory and logs changes to a file:

  const fs = require('fs');
  const chokidar = require('chokidar');

  const logFile = './log.txt';

  const log = msg => {
    fs.appendFile(logFile, msg + '\n', err => {
      if (err) throw err;
    });
  };

  const watcher = chokidar.watch('./dir-to-watch', {
    ignored: /^\./,
    persistent: true
  });

  watcher
    .on('add', path => log(`File ${path} has been added`))
    .on('change', path => log(`File ${path} has been changed`))
    .on('unlink', path => log(`File ${path} has been removed`))
    .on('error', error => log(`Watcher error: ${error}`))
    .on('ready', () => log('Initial scan complete. Ready for changes'));

In this example, any changes detected in ./dir-to-watch will be logged to log.txt.

By leveraging the capabilities of Chokidar, you can efficiently monitor and respond to file system changes within your Node.js applications.

Hash: 9365374aff724ca31cca071cb8ee294cc98603fcd07ce9454dd396ab9c66ae96