Create a readable stream

Q: Create a readable stream

const { Readable } = require('stream'); // Create a custom Readable stream class CustomReadableStream extends Readable { constructor(options) { super(options); this.currentIndex = 0; } _read() { if (this.currentIndex < 5) { const chunk = `Chunk ${this.currentIndex++}\n`; this.push(chunk); // Push data into the stream } else { this.push(null); // Signal the end of the stream } } } const readableStream = new CustomReadableStream(); //Alternatively, if you want to read from a file: const fs = require('fs'); const readableStream = fs.createReadStream('example.txt', { encoding: 'utf8' }); Using Event Listeners: readableStream.on('data', (chunk) => { console.log(`Received: ${chunk}`); }); readableStream.on('end', () => { console.log('Stream ended.'); }); //You can pipe the readable stream's data into a writable stream: const fs = require('fs'); const writableStream = fs.createWriteStream('output.txt'); readableStream.pipe(writableStream); //Using Async Iterators: This is the most modern and elegant way to consume streams in Node.js: (async () => { for await (const chunk of readableStream) { console.log(`Chunk: ${chunk}`); } console.log('Stream finished.'); })();

Difficulty: 5/10

custom readable streams, backpressure, stream piping

Here's how you can do it:

A readable stream is typically used to handle input, such as reading from a file or generating data programmatically. For example:

Readable streams can be consumed in three ways: using event listeners, the method, or async iterators. Here are examples:

Scenario Questions

0-2 years experience

1How would you implement a simple readable stream that emits the numbers 1 through 10?
2If you pipe that readable stream into a writable file stream and the file system is slower than the data generation, what does Node do?

2-5 years experience

1We need to process a large CSV file line‑by‑line without loading it all into memory. How would you set up a readable stream for this, and which options would you tune?

Follow-up Questions