JavaScript Fundamentals

JavaScript is a versatile programming language that runs in browsers and servers. Understanding its core concepts is essential for modern web development.

Variables and Data Types

JavaScript supports various data types:

• Primitive types: string, number, boolean, null, undefined, symbol
• Reference types: objects, arrays, functions

let message = "Hello World";
const age = 25;
const isActive = true;

Functions

Functions are first-class citizens in JavaScript:

// Function declaration
function greet(name) {
  return `Hello, ${name}!`;
}

// Arrow function
const add = (a, b) => a + b;

Key Concepts

• Hoisting: Variable and function declarations are moved to the top
• Closures: Functions have access to outer scope variables
• Prototype Chain: Objects inherit from other objects

Related Topics

This connects to async-programming and testing-strategies concepts.

See also: react/hooks-deep-dive for React-specific JavaScript patterns.

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