Difference between readFile and createReadStream in Node.js

Node.js offers various methods for file handling, two of the most commonly used being readFile and createReadStream. fs.readFile and fs.createReadStream are both used to read files in Node.js, but they cater to different needs. fs.readFile reads the entire file into memory, making it suitable for smaller files. In contrast, fs.createReadStream reads the file in chunks, which is more efficient for handling larger files.

Introduction to File Handling in Node.js

File handling in Node.js is an essential part of many applications, whether you're dealing with configuration files, logging data, or processing user uploads. The fs module in Node.js provides a plethora of methods to handle files, among which readFile and createReadStream are particularly significant.

Overview of readFile

readFile is a method that reads the entire contents of a file into memory. It is synchronous or asynchronous, depending on the function used (fs.readFileSync for synchronous or fs.readFile for asynchronous).

Syntax:

fs.readFile( filename, encoding, callback_function)

Parameters:

• filename: It holds the path to the file which has to be read.
• encoding: It holds the encoding of the file. If no option is specified, then the raw buffer is returned, Default value is 'utf8'.
• callback_function: It is a function that gets called after reading the file and contains two parameters err and data. If any error is encountered then it gets stored in err else content of the file is stored in data.

Return Value:

It returns the content of a file.

Characteristics

• Entire File in Memory: readFile reads the whole file content at once and loads it into memory.
• Callback or Promise-Based: The method supports both callback and promise-based asynchronous execution.
• Simple API: It provides a straightforward and simple API for file reading tasks.

Example: In this example, we are reading the file using the readFile method, File to be read is output.txt.

output.txt file:

This is an output file read from readFile method.

// app.js

const fs = require('fs');
fs.readFile('output.txt', 'utf8', (err, data) => {
  console.log(`Data present in the file is::    ${data}`);
});
console.log('Outside readFile method');

Output:

Outside readFile method
Data present in the file is::   
This is an output file read from readFile method.

Overview of createReadStream

createReadStream is a method that creates a readable stream for a file. It reads the file in chunks and emits them sequentially, which allows for handling large files efficiently.

Syntax:

fs.createReadStream(path, options)

Parameters:

• path: It holds the path to the file which has to be read. It could be the string, URL of the buffer.
• options: It is an optional parameter. We can pass a string or object to it.
• Return Value: It returns the object of ReadObject Stream.

Characteristics

• Streaming Data: createReadStream reads the file in chunks and streams the data, reducing memory usage.
• Event-Based: It operates using events like data, end, and error to handle the reading process.
• Efficient for Large Files: Ideal for reading large files that do not fit into memory

Example: In this example, We are reading file name output.txt by createReadStream.on method.

Output.txt file:

This is an output file read from createReadStream method.

// app.js

const fs = require('fs');
const createReader = fs.createReadStream('output.txt');

createReader.on('data', (data) => {
  console.log(data.toString());
});

console.log('Outside createReader.on method');

Output:

Outside createReader.on method
This is an output file read from createReadStream method.

Difference between readFile and createReadStream

Conclusion

Understanding the differences between readFile and createReadStream is vital for effective file handling in Node.js. While readFile offers simplicity and convenience for small files, createReadStream provides efficiency and scalability for handling larger files. By selecting the appropriate method based on your use case, you can optimize performance, manage memory usage effectively, and ensure your application runs smoothly.