Introduction to Readable-Stream

The readable-stream module in Node.js is an essential component when working with stream-based data. It provides a set of APIs to handle reading and interacting with data streams efficiently. Whether you are dealing with file streams, HTTP requests, or any other type of stream, the readable-stream module can significantly enhance your data processing tasks.

Key APIs in Readable-Stream

Creating a Readable Stream

To create a readable stream, you can use the Readable class:

  const { Readable } = require('readable-stream');
const readable = new Readable({
  read(size) {
    this.push('Hello, Stream!');
    this.push(null);
  }
});
readable.pipe(process.stdout);  

Piping Data

Piping is a technique to pass data from one stream to another. It is commonly used for connecting readable streams to writable streams:

  const { Readable, Writable } = require('readable-stream');
const readable = new Readable({
  read() {
    this.push('Stream data!');
    this.push(null);
  }
});
const writable = new Writable({
  write(chunk, encoding, callback) {
    console.log(chunk.toString());
    callback();
  }
});
readable.pipe(writable);  

Handling Stream Events

Streams in Node.js emit several events like data, end, and error. Here’s how you can handle these events:

  const { Readable } = require('readable-stream');
const readable = new Readable({
  read() {
    this.push('Event-driven stream data!');
    this.push(null);
  }
});
readable.on('data', (chunk) => {
  console.log('Received data:', chunk.toString());
});
readable.on('end', () => {
  console.log('Stream ended.');
});
readable.on('error', (err) => {
  console.error('Stream error:', err);
});
readable.pipe(process.stdout);  

Sample Application Using Readable-Stream

Let’s create a simple application that reads data from a file, processes it, and writes the results to another file:

  const fs = require('fs'); const { Transform } = require('readable-stream');
const readStream = fs.createReadStream('input.txt'); const writeStream = fs.createWriteStream('output.txt');
const transformStream = new Transform({
  transform(chunk, encoding, callback) {
    this.push(chunk.toString().toUpperCase());
    callback();
  }
});
readStream
  .pipe(transformStream)
  .pipe(writeStream)
  .on('finish', () => {
    console.log('Transformation complete. Check output.txt.');
  });
 

Conclusion

The readable-stream module in Node.js is a powerful tool for handling stream data. With the above examples and API explanations, you can optimize your data processing tasks and implement robust stream-based applications. Dive deeper into the module’s documentation to discover even more capabilities and advanced usages.

Hash: 88369504f3f6e71ea4c90744ee9194f6b241ba5f469cb3b517f83bc460bded34