is-stream 
Check if something is a Node.js stream
Install
$ npm install --save is-stream
Usage
const fs = require('fs');
const isStream = require('is-stream');
isStream(fs.createReadStream('unicorn.png'));
//=> true
isStream({});
//=> false
API
isStream(stream)
isStream.writable(stream)
isStream.readable(stream)
isStream.duplex(stream)
isStream.transform(stream)
License
MIT © Sindre Sorhus