Writing data with Writable streams in Node.js - Mini Project: Build & Apply

Writing data with Writable streams

📖 Scenario: You are building a simple Node.js program that writes some text data to a file using a writable stream. This is useful when you want to save logs or output data efficiently.

🎯 Goal: Create a writable stream to a file called output.txt and write three lines of text data to it using the stream's write method. Then close the stream properly.

📋 What You'll Learn

Create a writable stream to a file named output.txt

Write exactly these three lines to the stream: 'First line\n', 'Second line\n', 'Third line\n'

Close the writable stream using the end() method

💡 Why This Matters

🌍 Real World

Writable streams are used in Node.js to efficiently write data to files, network sockets, or other destinations without loading everything into memory at once.

💼 Career

Understanding writable streams is important for backend developers working with file systems, logging, or streaming data in Node.js applications.

1

Create a writable stream

Write a line to import the fs module and create a writable stream called writeStream that writes to a file named output.txt.

Node.js

const fs = require('fs');
// Create a writable stream called writeStream to 'output.txt'
// Your code here

Need a hint?

Use require('fs') to import the file system module. Then use fs.createWriteStream('output.txt') to create the stream.

2

Write the first line to the stream

Use the writeStream.write() method to write the string 'First line\n' to the stream.

Node.js

const fs = require('fs');
const writeStream = fs.createWriteStream('output.txt');
// Write 'First line\n' to writeStream
// Your code here

Need a hint?

Call writeStream.write() with the exact string 'First line\n'.

3

Write the second and third lines

Write the strings 'Second line\n' and 'Third line\n' to writeStream using the write() method twice.

Node.js

const fs = require('fs');
const writeStream = fs.createWriteStream('output.txt');
writeStream.write('First line\n');
// Write 'Second line\n' and 'Third line\n' to writeStream
// Your code here

Need a hint?

Call writeStream.write() two more times with the exact strings 'Second line\n' and 'Third line\n'.

4

Close the writable stream

Call the end() method on writeStream to close the stream properly.

Node.js

const fs = require('fs');
const writeStream = fs.createWriteStream('output.txt');
writeStream.write('First line\n');
writeStream.write('Second line\n');
writeStream.write('Third line\n');
// Close the writeStream
// Your code here

Need a hint?

Use writeStream.end() to close the stream after writing.