Reading files with promises (fs.promises) in Node.js - Mini Project: Build & Apply

Reading Files with Promises using fs.promises in Node.js

📖 Scenario: You are building a simple Node.js script to read the contents of a text file asynchronously. This is useful when you want your program to keep working without waiting for the file to finish loading.

🎯 Goal: Learn how to use fs.promises to read a file asynchronously and handle the content using promises.

📋 What You'll Learn

Create a variable to import the fs/promises module.

Create a variable with the exact filename example.txt.

Use fs.readFile to read the file content as a string.

Add a .then() method to handle the file content.

Add a .catch() method to handle any errors.

💡 Why This Matters

🌍 Real World

Reading files asynchronously is common in Node.js applications to avoid blocking the program while waiting for file operations. This helps keep apps responsive.

💼 Career

Understanding how to use promises with fs.promises is important for backend developers working with Node.js to handle file input/output efficiently.

1

Import fs.promises and set filename

Create a variable called fs that imports the fs/promises module using import. Then create a variable called filename and set it to the string 'example.txt'.

Node.js

import fs from 'fs/promises';
// Your code here

Need a hint?

Use import fs from 'fs/promises' to get the promises API of fs. Then assign filename to 'example.txt'.

2

Read the file content with readFile

Use fs.readFile with the variable filename and the option { encoding: 'utf8' } to read the file content as a string. Assign the returned promise to a variable called filePromise.

Node.js

import fs from 'fs/promises';
const filename = 'example.txt';
// Your code here

Need a hint?

Call fs.readFile(filename, { encoding: 'utf8' }) and assign it to filePromise.

3

Handle the file content with then

Add a .then() method to filePromise that takes a parameter called content and returns content. Assign this to a variable called contentPromise.

Node.js

import fs from 'fs/promises';
const filename = 'example.txt';
const filePromise = fs.readFile(filename, { encoding: 'utf8' });
// Your code here

Need a hint?

Use filePromise.then(content => content) and assign it to contentPromise.

4

Add catch to handle errors

Add a .catch() method to contentPromise that takes a parameter called error and returns the string 'Error reading file'. Assign this to a variable called finalPromise.

Node.js

import fs from 'fs/promises';
const filename = 'example.txt';
const filePromise = fs.readFile(filename, { encoding: 'utf8' });
const contentPromise = filePromise.then(content => content);
// Your code here

Need a hint?

Use contentPromise.catch(error => 'Error reading file') and assign it to finalPromise.