An Introduction to JavaScript

What is JavaScript?

JavaScript is a core web development technology alongside HTML and CSS.
- HTML structures web content.
- CSS manages styling and layout.
- JavaScript adds interactivity, logic, and advanced features.
Created by Brendan Eich in 1995 for Netscape Navigator.
Enhances web pages with interactivity and dynamic content.
Typical use cases:
- Form validation
- Animations and transitions
- Interactive content
- Fetching and displaying data
Can be used for client-side and server-side scripting.

Use the <script> tag to include JavaScript in HTML.
Best practice: Place JavaScript at the bottom of HTML pages.
Example code: <!DOCTYPE html> <html> <head> <title>My First JavaScript</title> </head> <body> <h2>My First JavaScript Program</h2> <button onclick="displayMessage()">Click me</button> <p id="demo"></p> <script> function displayMessage() { document.querySelector('#demo').textContent = 'Welcome to your first JavaScript program.'; } </script> </body> </html>

Variables: var, let, const
- let and const preferred over var for block scoping and immutability.
Data Types: Number, String, Boolean, Symbol, Object
- Numbers: Integers and floating-point numbers
- Strings: Text enclosed in quotes
- Booleans: true or false
- Symbols: Unique identifiers
- Objects: Containers for values and functions
Operators:
- Arithmetic: +, -, *, /, %
- Logical: &&, ||, !
- Comparison: ==, ===, !=, !==, <, >, <=, >=
- Compound: +=, -=, *=, /=

Conditional Statements:
- if/else: Execute code blocks based on conditions.
- Nested if: Check multiple conditions.
- Ternary operator: Shorthand for if/else.
Loops:
- while: Repeatedly execute a block as long as a condition is true.
- for: Execute a block a specific number of times.
- for...of: Iterate over iterable objects like arrays.

Organizes code using objects with properties and methods.
Classes: Blueprints for creating objects.
- Use class keyword and constructor method.
Inheritance: Allows a class to inherit properties/methods from another.
Methods: Functions associated with an object.

Reusable code performing specific tasks.
Types:
- Function Declarations: function myFunction() {}
- Function Expressions: const myFunc = function() {}
- Arrow Functions: const myFunc = () => {}

Arrays: Store multiple values in a single variable.
- Methods: push, pop, shift, slice
Maps and Sets:
- Maps: Key-value pairs with any data type as key.
- Sets: Collections of unique values.

Benefits:
- Reduced development time
- Improved code maintainability
- Access to community resources
Popular Examples:
- jQuery, React, Angular, Node.js