<h2>Introduction to the course</h2>Node.js Advanced is a course we&#x27;ve created to introduce the more complex side of development.<h2>Who is this course for?</h2>If you&#x27;re a developer with the basic and fundamental concepts of Node.js down, then this course is meant for you to discover the uncharted lands of Node.js.<h2>Recommendations for the course:</h2>Make sure you&#x27;ve completed our Node.js course to ensure the strong foundation you&#x27;ll be needing here.

Node.js Advanced

<h2>What does this lesson cover?</h2>The fixed area of the memory we call the Buffer class will be the topic of this lesson.Accessing the Buffer class is accessible without importing as it is a part of the Buffer Module, a core Node.js Module.The question we&#x27;ll answer is why exactly developers need to incorporate Buffers in code. Thus, we&#x27;ll create Buffers, write to Buffers, copy and decode Buffers, slice Buffers, and define Buffer Bytes.

Buffers

<h2>What does this lesson cover?</h2>We&#x27;ve referred to the fs module multiple times in the past lessons, however, the short description we&#x27;ve provided does not suffice and simply does not align with the importance of the fs module.This introduction scratches the service of the module that stores all the file query, manipulation functions and gives developers access to working with their computer’s file system.

Introduction

<h2>What does this lesson cover?</h2>The Understanding Streams lesson defines the usage and purpose of Streams and differentiates between the two types of Streams– Readable Streams and Writable Streams, Transform Streams, and Duplex Streams.We&#x27;ll also be expanding on the widely used mechanisms of Piping Streams and Chaining Streams by identifying where and how to use them in your Node.js application.

Understanding Streams

<h2>What does this lesson cover?</h2>This lesson covers a standard method of the fs module that has wide usage in Node.js applications by opening a file and thus allowing the reading and manipulating processes. We&#x27;ll also be identifying the elated concept of flags with corresponding examples that depict their usage.

Open a File

<h2>What does this lesson cover?</h2>File uploads take place when a user sends a request from a client machine to the server. This process is supported in Node.js with the help of the third-party Formidable Module.The said module permits various file uploads that we will be referring o in this lesson. With the help of the methods described in the lesson, developers will be able to upload forms, parse URLs, and save files.

Upload Files

<h2>What does this lesson cover?</h2>Information concerning the size of a file for example, or file permissions, and other characteristics that describe files are common info that developers might need to get their hands on at some point in time.This lesson covers the steps developers need to take to get that information with the help of methods you can find in the fs module.

Get File Information

<h2>What does this lesson cover?</h2>Sometimes, inputting a URL and a callback function is all you need to make a request. That said, the best approach may not always align with simple steps.The Request module covers advanced cases when making a request in Node.js.After learning how to install the Request Module we&#x27;ll use it in our Node.js application to create servers, follow redirects, etc.Each action is depicted in separate lessons with supporting examples and quizzes.

Request Module

Lesson Challenge

<h2>What does this lesson cover?</h2>There are a lot of ways for file reading, closing a file and file writing in Node.js. In this lesson, we&#x27;ll refer to the simplest and most efficient of the bunch in both cases.The methods described in the lesson will further develop your skills to work with files in Node.js.

Writing/Reading and Closing a File

<h2>What does this lesson cover?</h2>Node.js permits us to code an application for mail exchanges through third-party modules that require installation with the npm (Node Package Manager).This lesson will cover the exact syntax and structure of the said third-party module, thus, we&#x27;ll get into the process of incorporating that module into code and sending emails with our Node.js application.

Email

<h2>What does this lesson cover?</h2>Manipulating files in Node.js is standard practice, we&#x27;ve already assessed some methods regarding access properties, and now it&#x27;s time to learn how to truncate and delete Node.js files.The phrase truncate indicates changing the size of your Node.js files. In this lesson, we&#x27;ll assess the method used to truncate files, their syntax, and structure in code.Deleting files requires the use of a separate method that we&#x27;ll be referring to also.

Truncate and Delete a File

<h2>What does this lesson cover?</h2>Creating a directory in Node.js requires a sequence of steps which we&#x27;ll be analyzing in the following lesson.We&#x27;ll also be expanding on the reading, writing, and removing directories from your Node.js application. Each action requires a separate approach that we&#x27;ll digest in individual lessons with supporting code examples and quizzes.

Directories and methods

Streams, Readable 

In Node.js Streams are a core concept and represent objects that permit continuous data reading from a source or data writing to a specified destination. There are 4 types to refer to: Writable, Readable, Duplex, and Transform. Each listed type is an EventEmitter instance, so they shoot over multiple events at different time instances. Events such as- data, error, finish, end.

The EventEmitter module will be further elaborated on in future lessons.

The Streams used in Node.js are −

Readable streams are a source of data consumption. Concerning practical purposes, to create a readable Stream and build on top of it, we&#x27;ll be working with the following examples.

The first steps in setting up your Readable Stream are utilizing a File System (fs), creating a file, setting an encoder (UTF8-8, for better results), and working with stream events (end, data, error, close, pause, etc.).

Examples &amp; Explanations of common Stream Events:

<ul><li>End: The &#x27;end&#x27; event indicates the end of readable information from the stream.</li><li>Data: &#x27;data&#x27; event indicated the stream giving up ownership of a chunk of data to the user.</li><li>Error: indicated the inability of data generation by the stream.</li><li>Finish: Indicated that underlying stream resources (file descriptors) have been closed.</li></ul>

Fill Missing

Node.js fs module

In the Readable Stream code implementation, there was the usage of the <samp>fs</samp> module. The usage of the <samp>fs</samp> module depends on its functionality methods to access and interact with the file system. The module is a staple method when running Streams. Installing <samp>fs</samp> is not necessary as it is a part of the core Node.js and utilizing it involves calling it as performed in the Readable Stream section.

After called for you&#x27;ll be granted access to all its methods including and not limited to:<ul><li><code><samp>fs.access()</samp></code> for checking if a file exists and is accessible by Node.js </li><li><code><samp>fs.appendFile()</samp></code> for appending data to a file and if the said file doesn&#x27;t exist it&#x27;ll be created</li><li><code><samp>fs.chown()</samp></code> change the owner and group of a file specified by the filename passed</li><li> <code><samp>fs.chmod()</samp></code> changing permissions of a file specified by the filename passed</li><li><code><samp>fs.link()</samp></code> creating a hard link to a file</li><li><code><samp>fs.copyFile()</samp></code> for copying a file</li><li><code><samp>fs.createReadStream() </samp></code> creating a readable file stream</li><li><code><samp>fs.createWriteStream()</samp></code>creating a writable file stream</li><li><code><samp>fs.close()</samp></code> for exiting a file descriptor</li><li><code><samp>fs.mkdir()</samp></code> creating a new folder</li></ul>

Select Correct Answer

What is the functionality of the <samp>fs.chmod()</samp> method?

Writable Streams

Writable Streams are one of the four types of streams Node.js proposes and are the defining factor of your written data (its destination e.g. a file). The output of a Readable Stream can be considered the input of a Writable Stream. While specific instances of Writable Streams differ in key ways (events), the fundamental usage of the Stream remains, while following the basic structure of the Readable stream.

The result when you open the command prompt will be <samp>&quot;output.txt&quot;</samp> and the four rhetorical modes.

The Stream events used above are <code><samp>&#x27;error&#x27;</samp></code> <code>(</code>called in case an error occurred while writing) and <code><samp>&#x27;finish&#x27;</samp></code> (called after all data has been flushed to an underlying system.

Streams aren&#x27;t always a necessity and in those cases, you may lose the simplicity of your application. Weighing the benefits Streams bring at all times is crucial.

Which of the following statements is true?

Duplex Streams

Duplex Streams implement both the <samp><code>Readable</code></samp> and <samp><code>Writable</code></samp> interfaces. A prime example of Duplex Streams is a Socket. Sockets provide two passages for sending and receiving information. Other examples of Duplex Streams are TCP sockets, zlib streams, and crypto streams.

When creating a Duplex Stream, start off by implementing the required methods (File System), we’ll be utilizing the PassThrough Stream which is a standard version of Duplex and acts as a connecting tunnel between Readable Stream and Writable Stream. The next step is reading a file and including it into a Writeable Stream with WriteStream.

Duplex Streams stand between pipes and give developers a full view of the data flowing in between.

Transform Streams

Transform Streams are a form of Duplex Streams, meaning, they implement both <samp> Readable </samp>and <samp>Writable</samp> passages, the main difference is that the output is always connected to the input. When creating a Transform Stream, firstly import the required methods (Transform class, File System) and begin creating.

We’ve created a Transform Stream with the following event results: the <samp>chunk</samp> of data, in case the chunk is a string we&#x27;ve implemented <samp>encoding</samp>, and finally a <samp>callback</samp> for retrieval of results. Running the code will result in all text in the file to lowercase and writing it to <samp>transformedData.txt</samp>

What&#x27;s the difference between Duplex Streams and Transform Streams?

Piping Streams

Piping Streams is a mechanism where an output of one Stream plays the input role for another Stream. In simpler terms, piping connects multiple Streams together. The importance of piping is its ability to break down complex processing into simplified and smaller tasks that result in separate execution. Node.js provides the <samp>pipe</samp> method for that purpose.

A typical example of a Piping Stream in action is connecting files. i.e. transfering data from file-to-file. In the code-snippet below, assume you have a file under the name dataInput.txt that has data stored inside. With the help of the pipe method we&#x27;ll be copying that data into an empty dataOutput.txt.

By using the piping method we get dataOutput.txt and dataInput.txt containing the same data.

Chaining Streams

The Chaining stream is for the creation of a chain of many Stream functions by connecting an output of one stream to another. This Stream is usually associated with the piping operation. In the example code snippets, we&#x27;ll compress and thus decompress the same file.

After running the current directory will have already stored the compressed file. The next step is decompressing that same file by utilizing piping and the Chaining Stream.

Chaining Streams through piping affects the entire flow of your application and simplifies execution processing. The <samp>pipe </samp>method manages a couple of tasks simultaneously, which could include end-of-files, slow streams, errors, etc. without consuming time and additional resources.

The Chaining Stream is associated with the...

<h2>What does this section cover?</h2>The incorporation of Buffers and Streams in React applications is a crucial step and this section covers the questions why? and how?After defining the buffers and everything developers can do with Buffers, we&#x27;ll introduce Streams, the types of Streams, and the fs module that is a requirement for using Streams.

Streams

<h2>What does this section cover?</h2>The Node.js File System stores all the file query, manipulation functions and gives developers access to working with their computer’s file system.This section covers the wide range of opportunities that the fs module offers developers to incorporate into their advanced Node.js code.We&#x27;ll be referencing different file manipulation methods, directories, access methods, but only after covering the basic operations and techniques.

File System

<h2>What does this section cover?</h2>Working with Node.js does not always entail limitations regarding core/built-in modules. In some cases, developers are meant to use third-party modules and packages to complete their application or incorporate features into their applications that are not available in the core/built-in Modules.This section will focus on uploading files, requests, and emailing with the help of packages.