Lecture Notes on JavaScript

Overview

• JavaScript is a versatile programming language capable of creating a variety of applications:
  • Web applications (front-end and back-end)
  • Mobile applications
  • Desktop applications
  • Machine learning applications
• Initially released in 1995 for web front-end purposes.
• Developed by Netscape in collaboration with Sun Microsystems.
• JavaScript's capability has expanded beyond the web front-end to back-end, mobile, desktop, and machine learning because of its ease and widespread developer support.
• Node.js allows JavaScript to run on the OS, enabling back-end and other applications.

JavaScript History

• Early 1990s: Websites were static and non-interactive.
• 1993: Mosaic browser popularized web browsing.
• Netscape Navigator: Introduced JavaScript in 1995 to bring interactivity to web pages.
• JScript: Microsoft's reverse-engineered version of JavaScript.
• ECMAScript Standard: Established in 1997 for standardizing JavaScript implementations.
• 2008: Google Chrome introduced V8 engine with Just-In-Time compilation, enhancing JavaScript speed.
• Node.js: Introduced to allow JavaScript to run outside the browser on the OS.

JavaScript as a Programming Language

• JavaScript is among the top five programming languages globally, as per various articles.
• 97% of websites use JavaScript for the client side.
• Oracle owns the JavaScript trademark.

Learning and Using JavaScript

• It's essential to practice coding and experiment with JavaScript on your machine.
• JavaScript is not just for web but should be treated as a versatile programming language.
• The course will teach JavaScript from start to end, including running JavaScript directly on the machine using Node.js and VS Code.

Setting up Development Environment

1. Node.js: Required for running JavaScript on the OS.
2. VS Code: Editor for writing and running JavaScript code.
3. Learn to use terminal for running JavaScript files.
4. Use extensions like Code Runner to simplify running and debugging code.

Basic JavaScript Concepts

• Variables & Constants:

  • Variables store temporary data; constants store unchangeable data.
  • let and const are used for declaring variables and constants, respectively.

• Data Types:

  • Primitive: Number, String, Boolean, Null, Undefined, Symbol.
  • Object: Complex data types not covered in primitive.

• Operators:

  • Arithmetic: +, -, *, /, %, etc.
  • Relational: <, >, <=, >=, ==, ===, etc.
  • Logical: && (and), || (or), ! (not).

• Control Structures:

  • If-Else: For decision making.
  • Switch-Case: For handling multiple conditions.
  • Loops: For repeating operations (for, while, do-while).*

Functions

• Declaration: Functions can return values and accept parameters.
• Expression: Assign a function to a variable for anonymous functions.
• Arrow Functions: Simplified syntax for anonymous functions.
• Recursion: Functions that call themselves.

Object-Oriented JavaScript

• Objects & Methods:
  • Objects store key-value pairs.
  • Methods are functions within objects.
  • this keyword: Refers to the current object instance.
• Constructors: Functions to create multiple object instances.
• Inheritance and Prototypes: Advanced concepts for object creation.

Advanced JavaScript Concepts

• Arrays: Collection of data with methods such as push, pop, etc.
• Array Methods: forEach, map, filter, reduce, etc.
• Set: Collection of unique values.
• Map: Collection of key-value pairs.
• Deconstruction: Extract values from arrays or objects for easier manipulation.

JavaScript in Practice

• Explore writing clean, efficient, and error-free code.
• Understand debugging and error handling.
• Experiment with different paradigms and applications using JavaScript.