Watching files for changes in Node.js - Mini Project: Build & Apply

Watching Files for Changes with Node.js

📖 Scenario: You are building a simple Node.js script that watches a specific file for any changes. This is useful when you want your program to automatically react whenever the file content updates, like reloading configuration or processing new data.

🎯 Goal: Create a Node.js script that watches a file named data.txt in the current folder. When the file changes, the script should print a message indicating the file was updated.

📋 What You'll Learn

Create a variable for the file path data.txt

Create a configuration variable for the watch options

Use fs.watch to watch the file for changes

Add a callback function that logs a message when the file changes

💡 Why This Matters

🌍 Real World

Watching files for changes is useful in development tools, live reload servers, and automation scripts that need to react immediately when files update.

💼 Career

Many backend and DevOps roles require knowledge of file system watchers to build efficient workflows and monitoring tools.

1

Set up the file path variable

Create a constant variable called filePath and set it to the string './data.txt'.

Node.js

# Your code here

Need a hint?

Use const to create a variable that holds the file path string.

2

Add watch options configuration

Create a constant variable called watchOptions and set it to an object with the property persistent set to true.

Node.js

const filePath = './data.txt';
# Your code here

Need a hint?

The persistent option keeps the process running while watching.

3

Use fs.watch to watch the file

Import the fs module using import fs from 'fs';. Then use fs.watch with filePath, watchOptions, and a callback function with parameters eventType and filename.

Node.js

const filePath = './data.txt';
const watchOptions = { persistent: true };
# Your code here

Need a hint?

Use ES module import syntax and pass the correct arguments to fs.watch.

4

Log a message when the file changes

Inside the fs.watch callback, add an if statement that checks if eventType is 'change'. If true, log the message File data.txt was updated using console.log.

Node.js

import fs from 'fs';
const filePath = './data.txt';
const watchOptions = { persistent: true };
fs.watch(filePath, watchOptions, (eventType, filename) => {
    # Your code here
});

Need a hint?

Use a strict equality check and console.log inside the callback.