let Readble = require('stream').Readable;
let r = new Readble;
let count = 0;

r._read = function() {
    count++;
    if(count > 10) {
        return r.push(null);
    }
    setTimeout(() => r.push(count + '\n'), 500);
}
r.pipe(process.stdout);

stream2file.js

let Readble = require('stream').Readable;
let r = new Readble;
let count = 0;
const fs = require('fs');

const w = fs.createWriteStream('./counter.txt', {flags:'w', mode: 0666});

r._read = function() {
count++;
if(count > 10) {
return r.push(null);
}
setTimeout(() => r.push(count + '\n'), 500);
}

r.pipe(w);