02_NodeJS_Notes.md

globalThis is a global object in JavaScript that provides access to the global scope. It is available in both browser and Node.js environments, allowing you to define and access global variables and functions.

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History of Nodejs

Node.js was created by Ryan Dahl in 2009. It is built on the V8 JavaScript engine, which is also used by Google Chrome. Node.js allows developers to use JavaScript for server-side programming, enabling the creation of scalable and high-performance applications.

io.js was a fork of Node.js that emerged in 2014, focusing on faster releases and new features. In 2015, io.js merged back into the Node.js project, leading to the current version of Node.js.

In 2019, Node.js was officially adopted by the OpenJS Foundation, which is part of the Linux Foundation. This move aimed to ensure the long-term sustainability and growth of the Node.js project.

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Basic Shell Commands

• echo command used in the terminal is a command-line utility that outputs the strings it is being passed as arguments. It is commonly used to display messages or to write text to files.

• To print the variables in terminal, you can use the echo command followed by the variable name. For example, if you have a variable named myVar, you can print it in the terminal using:

echo $myVar

adding two variables in the terminal can be done using the echo command as well. For example, if you have two variables var1 and var2, you can add them and print the result like this:

var1=5
var2=10
echo $((var1 + var2))

• pwd command is used to print the current working directory in the terminal. It displays the full path of the directory you are currently in.

• whoami command is used to display the username of the current user logged into the terminal. It shows the name of the user who is currently executing commands in the shell.

• cd command is used to change the current directory in the terminal. It allows you to navigate to different directories in the file system. For example, to change to a directory named myFolder, you would use:

cd myFolder

• ls command is used to list the files and directories in the current directory. It provides a view of the contents of the directory you are currently in. You can use it like this:

• mkdir command is used to create a new directory in the terminal. It allows you to create a folder with a specified name. For example, to create a directory named newFolder, you would use:

mkdir newFolder

• rm command is used to remove files or directories in the terminal. It allows you to delete files or folders. For example, to remove a file named file.txt, you would use:

rm file.txt

• rmdir command is used to remove empty directories in the terminal. It allows you to delete a directory only if it is empty. For example, to remove an empty directory named emptyFolder, you would use:

rmdir emptyFolder

• cp command is used to copy files or directories in the terminal. It allows you to create a duplicate of a file or folder. For example, to copy a file named source.txt to a new file named destination.txt, you would use:

cp source.txt destination.txt

• mv command is used to move or rename files and directories in the terminal. It allows you to change the location of a file or folder or rename it. For example, to move a file named file.txt to a directory named myFolder, you would use:

mv file.txt myFolder/

PS1 and PS2 in bash

PS1 and PS2 are environment variables in the shell that define the appearance of the command prompt. PS1 is the primary prompt string, which is displayed when the shell is ready to accept a command. It can include various escape sequences to display information like the username, hostname, current directory, etc.

PS2 is the secondary prompt string, which is displayed when a command spans multiple lines. It is typically used to indicate that the shell is waiting for more input.

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