Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

const { Readable, Writable, Transform } = require('stream');

// --- Custom Readable stream ---
class NumberStream extends Readable {
    constructor(max) {
        super({ objectMode: true });
        this.current = 1;
        this.max     = max;
    }
    _read() {
        if (this.current <= this.max) {
            this.push(this.current++);
        } else {
            this.push(null); // Signal end of stream
        }
    }
}

// --- Custom Transform stream ---
class SquareTransform extends Transform {
    constructor() {
        super({ objectMode: true });
    }
    _transform(chunk, encoding, callback) {
        this.push(chunk * chunk);
        callback();
    }
}

// --- Custom Writable stream ---
class SumWritable extends Writable {
    constructor() {
        super({ objectMode: true });
        this.sum = 0;
    }
    _write(chunk, encoding, callback) {
        this.sum += chunk;
        callback();
    }
}

// Pipe them together:
const numbers = new NumberStream(5);  // 1 2 3 4 5
const squares = new SquareTransform(); // 1 4 9 16 25
const sum     = new SumWritable();     // 55

numbers.pipe(squares).pipe(sum);

sum.on('finish', () => {
    console.log('Sum of squares:', sum.sum); // 55
});