Node.js File Writing Methods - createWriteStream vs writeFileSync

When working with Node.js file system operations, choosing the right method to write files can significantly impact your application's performance. Let's explore two common approaches: fs.createWriteStream() and fs.writeFileSync().

Key Differences at a Glance

Feature	fs.createWriteStream(path).write(buffer)	fs.writeFileSync(path, buffer)
Synchronicity	Asynchronous	Synchronous
Blocking	Non-blocking	Blocking
Performance	Better for large files or frequent writes	Better for small, infrequent writes
Memory Usage	More memory-efficient for large files	Loads entire content into memory
Error Handling	Requires callback or event listeners	Throws errors directly
Use Case	Streaming large files, real-time data	Quick, simple writes, small files
Control Flow	Continues execution immediately	Waits until write is complete
Backpressure Handling	Handles backpressure automatically	N/A

Using createWriteStream

The stream-based approach is ideal for handling large files or when you need to write data frequently:

const fs = require('fs')
 
// Content to write
const content = 'Hello, Node.js file system!'
 
// Create a write stream
const writeStream = fs.createWriteStream('example1.txt')
 
// Write to the file
writeStream.write(content, 'UTF8')
 
// End the stream
writeStream.end()
 
// Handle finish event
writeStream.on('finish', () => {
  console.log('Write completed.')
})
 
// Handle error event
writeStream.on('error', (err) => {
  console.error('An error occurred:', err.message)
})
 
console.log('Program continues executing immediately.')

Key Benefits 🎯

Non-blocking operation
Memory efficient for large files
Automatic backpressure handling
Ideal for real-time data processing

Using writeFileSync

For simple, one-off writes with small files, the synchronous approach might be more straightforward:

const fs = require('fs')
 
// Content to write
const content = 'Hello, Node.js file system!'
 
try {
  // Write to the file synchronously
  fs.writeFileSync('example2.txt', content, 'UTF8')
  console.log('Write completed.')
} catch (err) {
  console.error('An error occurred:', err.message)
}
 
console.log('This line waits for the write operation to complete.')

Key Benefits 🎯

Simple error handling with try-catch
Predictable execution flow
Perfect for configuration files or small data writes
No callback management needed

When to Use Each Method

Choose createWriteStream when:

Working with large files
Handling real-time data streams
Memory efficiency is crucial
Non-blocking operation is required

Choose writeFileSync when:

Writing small configuration files
Simple, one-off writes
Synchronous operation is acceptable
Working with startup configurations

Conclusion

Both methods have their place in Node.js development. createWriteStream shines in scenarios involving large files or frequent writes, while writeFileSync is perfect for simple, small file operations. Choose based on your specific use case, considering factors like file size, write frequency, and performance requirements.