Поток дуплексный
const isDuplexStream = val => val !== null && typeof val === 'object' && typeof val.pipe === 'function' && typeof val._read === 'function' && typeof val._readableState === 'object' && typeof val._write === 'function' && typeof val._writableState === 'object';
const Stream = require('stream'); isDuplexStream(new Stream.Duplex()); // true