Node.js Module System: Common JS

Node.js File System (Fs) Module

• The Fs module in Node.js stands for "File System" and provides an API for interacting with the file system, modeled on standard POSIX functions.
• It allows you to work with files by performing various operations like reading, writing, and manipulating.
• Common Fs module functions include fs.readFileSync() and fs.writeFileSync().

JSON (JavaScript Object Notation)

• JSON is a lightweight data-interchange format that is plain text written in JavaScript object notation.
• It is used to send data between computers and is language independent.
• JSON has two main functions:
  • JSON.stringify(): Converts an object or array of objects to a JSON string, accepting any type of data and returning a string in JSON format.
  • JSON.parse(): Converts a string in JSON format to an object, accepting only strings in JSON format and throwing an error when trying to parse a string not in JSON format.

CLI (Command Line Interface) Example

• We can create a simple CRUD (Create, Read, Update, Delete) operation app that uses the file system to save data.
• We will use a JSON file as a database to store data about employees (name, salary).

Common JS Module System

• Node.js used the Common JS module system to break code into smaller chunks, which is still used today.
• The module system creates the ability to export and import JavaScript from separate files.
• require() is used to import modules, and destructuring is often used when only requiring one function from an otherwise large library.

Process and Timers

• The process module contains the ability to perform tasks immediately before the process exits, and when it exits.
• process.argv is an array containing your console information for your executed process.
• The Node.js timers API is similar, but not identical to the browser API.
• setImmediate() and clearImmediate() are used in Node.js.

Path Module

• The path module is used to normalize paths to work across platforms.
• path.resolve() enables you to get the absolute path from a relative path.
• path.normalize() normalizes any path by removing instances of . and .., turning double slashes into single slashes, and removing a directory when .. is found.
• path.join() is used to concatenate strings to create a path that works across operating systems.

Event Loop

• Node.js is a single-threaded, non-blocking, event-driven JavaScript runtime environment.
• Nearly every Node.js feature is considered to be asynchronous (non-blocking).
• The Event Loop is a process that runs anytime you have asynchronous code, allowing your application to continue running while requests are being waited for.
• The Event Loop is a continuously running, semi-infinite loop that runs for as long as there is a pending asynchronous operation.