como usar o isStream no javascript es6

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

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