Stream Is Duplex

Introduction

In this lab, we will explore how to determine whether a given argument is a duplex (readable and writable) stream in JavaScript. We will use a combination of typeof checks and property validations to create a function that can accurately identify duplex streams. By the end of this lab, you will have a better understanding of how streams work in JavaScript and how to work with them in your own code.

Skills Graph

Checking if a Stream is Duplex

To check if a stream is duplex (readable and writable), open the Terminal/SSH and type node to start practicing coding. Then, follow these steps:

1. Check if the given argument is different from null.
2. Use typeof to check if the given argument is of type object and if it has a pipe property of type function.
3. Additionally, check if the _read, _write, _readableState, and _writableState properties are of type function and object, respectively.

Here's the code:

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";

You can test this code using the following example:

const Stream = require("stream");

isDuplexStream(new Stream.Duplex()); // true

Summary

Congratulations! You have completed the Stream Is Duplex lab. You can practice more labs in LabEx to improve your skills.