Stream Is Writable

Introduction

In this lab, we will explore how to check if a given argument is a writable stream in JavaScript. We will use a function that checks if the value is different from null, if it has a pipe property of type function, and if it also has _write and _writableState properties of type function and object respectively. Through this lab, we will gain a better understanding of how to work with streams in JavaScript.

Skills Graph

Checking if a Stream is Writable

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

1. Check if the given argument is not null.
2. Use typeof to check if the value is an object and if the pipe property is a function.
3. Additionally, check if the typeof the _write and _writableState properties are function and object, respectively.

Here's an example code that implements these checks:

const isWritableStream = (val) =>
  val !== null &&
  typeof val === "object" &&
  typeof val.pipe === "function" &&
  typeof val._write === "function" &&
  typeof val._writableState === "object";

You can test this function using the fs module in Node.js. For example:

const fs = require("fs");

isWritableStream(fs.createWriteStream("test.txt")); // true

Summary

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