Module 5: Functions

Overview

Functions are fundamental building blocks in JavaScript. They allow you to encapsulate reusable code, organize your program, and implement complex logic. This module covers everything from basic function syntax to advanced concepts like closures, higher-order functions, and functional programming patterns.

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Module Contents

5.1 Function Declarations

• •Function syntax and hoisting
• •Named functions
• •Function scope basics

5.2 Function Expressions

• •Anonymous functions
• •Named function expressions
• •Expression vs declaration
• •Conditional function creation

5.3 Arrow Functions

• •Arrow syntax (=>)
• •Implicit returns
• •Lexical this binding
• •When to use arrow functions

5.4 Parameters and Arguments

• •Default parameters
• •Rest parameters (...args)
• •Destructuring in parameters
• •The arguments object

5.5 Call, Apply, and Bind

• •Explicit this binding
• •call() method
• •apply() method
• •bind() method
• •Method borrowing
• •Partial application

5.6 Scope and Closures

• •Global, function, and block scope
• •Lexical scope
• •Scope chain
• •Closures explained
• •Practical closure patterns
• •Module pattern

5.7 Higher-Order Functions

• •Functions as arguments
• •Functions as return values
• •map(), filter(), reduce()
• •forEach(), find(), some(), every()
• •Method chaining
• •Custom higher-order functions

5.8 Recursion

• •Base case and recursive case
• •Call stack and recursion
• •Classic examples (factorial, fibonacci)
• •Recursive data processing
• •Tail recursion
• •When to use recursion

5.9 Pure Functions and Side Effects

• •What makes a function pure
• •Identifying side effects
• •Benefits of pure functions
• •Immutability patterns
• •Managing side effects
• •Functional programming basics

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Learning Path

┌─────────────────────────────────────────────────────────┐
│                 MODULE 5: FUNCTIONS                      │
├─────────────────────────────────────────────────────────┤
│                                                          │
│  BASICS                                                  │
│  ├── 5.1 Function Declarations                          │
│  ├── 5.2 Function Expressions                           │
│  ├── 5.3 Arrow Functions                                │
│  └── 5.4 Parameters and Arguments                       │
│                                                          │
│  CONTEXT & SCOPE                                         │
│  ├── 5.5 Call, Apply, and Bind                          │
│  └── 5.6 Scope and Closures                             │
│                                                          │
│  ADVANCED PATTERNS                                       │
│  ├── 5.7 Higher-Order Functions                         │
│  ├── 5.8 Recursion                                      │
│  └── 5.9 Pure Functions & Side Effects                  │
│                                                          │
└─────────────────────────────────────────────────────────┘

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Key Concepts Summary

Function Types

Scope Types

Higher-Order Functions

Pure Functions

• •Same input → Same output
• •No side effects
• •Predictable and testable
• •Easy to memoize

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Practical Skills You'll Learn

1. •

   Writing Reusable Functions

   • •Proper parameter handling
   • •Default values and validation
   • •Clear return values
2. •

   Managing Context (this)

   • •Understanding this binding
   • •Using call, apply, bind
   • •Arrow functions for callbacks
3. •

   Closures for Data Privacy

   • •Private variables
   • •Module pattern
   • •Factory functions
4. •

   Functional Programming

   • •Data transformation with HOFs
   • •Method chaining
   • •Immutable operations
5. •

   Recursive Problem Solving

   • •Tree/nested data traversal
   • •Divide and conquer
   • •Algorithm design

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How to Use This Module

1. •Start with basics (5.1-5.4) if you're new to functions
2. •Study each section's README for concepts
3. •Run examples.js to see code in action
4. •Complete exercises.js to practice
5. •Check solutions when stuck

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Prerequisites

• •Variables and data types (Module 2)
• •Operators (Module 3)
• •Control flow (Module 4)

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Next Steps

After completing this module, you'll be ready for:

• •Module 6: Execution Model & Scope
• •Module 7: Objects
• •Module 12: ES6+ Classes
• •Module 14: Async JavaScript