Example of writable stream in NodeJS.

writable_stream.js

const stream = require('stream');
const fs = require('fs');

class EchoStream extends stream.Writable {
    _write(chunk, enc, next) {
        console.log(chunk.toString());
        next();
    }
}

const echoStream = new EchoStream();

fs.createReadStream('./test.txt').pipe(echoStream);