isStream

Checks if the given argument is a stream.

• Check if the value is different from null.
• Use typeof to check if the value is of type object and the pipe property is of type function.

const isStream = val =>
  val !== null && typeof val === 'object' && typeof val.pipe === 'function';

const fs = require('fs');

isStream(fs.createReadStream('test.txt')); // true