Why file system access matters in Node.js - See It in Action

Why file system access matters

📖 Scenario: You are building a simple Node.js app that reads and writes text files on your computer. This helps you understand why file system access is important for many real-world apps like note-taking, data logging, or configuration management.

🎯 Goal: Create a Node.js script that reads a text file, counts the number of words, and writes the count to a new file.

📋 What You'll Learn

Use the built-in fs module to read and write files

Read the contents of a file named input.txt

Count the number of words in the file content

Write the word count to a file named output.txt

💡 Why This Matters

🌍 Real World

Many apps need to read and save data on your computer, like text editors, loggers, or configuration tools. Understanding file system access lets you build these apps.

💼 Career

Node.js developers often work with files for data processing, automation, and backend services. Knowing how to use the file system module is a key skill.

1

Set up the file system module and read the file

Write import fs from 'fs/promises' to import the file system promises API. Then create an async function called countWords that reads the file input.txt using await fs.readFile('input.txt', 'utf-8') and stores the content in a variable called text.

Node.js

import fs from 'fs/promises'

async function countWords() {
  // Your code here
}

Need a hint?

Use import fs from 'fs/promises' to get the modern promise-based file system API. Use await fs.readFile inside an async function to read the file content as text.

2

Add a variable to count words

Inside the countWords function, create a variable called words that splits the text by spaces using text.split(' '). Then create a variable called wordCount that stores the length of the words array.

Node.js

import fs from 'fs/promises'

async function countWords() {
  const text = await fs.readFile('input.txt', 'utf-8')
  // Your code here
}

Need a hint?

Use text.split(' ') to break the text into words. Then use words.length to count how many words there are.

3

Write the word count to a new file

Still inside the countWords function, use await fs.writeFile('output.txt', `Word count: ${wordCount}`) to write the word count to a file named output.txt.

Node.js

import fs from 'fs/promises'

async function countWords() {
  const text = await fs.readFile('input.txt', 'utf-8')
  const words = text.split(' ')
  const wordCount = words.length
  // Your code here
}

Need a hint?

Use await fs.writeFile to save the word count string to output.txt.

4

Call the function to run the script

After the countWords function, add a line to call countWords() so the script runs when executed.

Node.js

import fs from 'fs/promises'

async function countWords() {
  const text = await fs.readFile('input.txt', 'utf-8')
  const words = text.split(' ')
  const wordCount = words.length
  await fs.writeFile('output.txt', `Word count: ${wordCount}`)
}

// Your code here

Need a hint?

Simply call countWords() after the function to run the code.