Strategy Pattern Guide

Core Principles

What is Strategy Pattern?

The Strategy Pattern enables selecting algorithms at runtime by encapsulating related operations into interchangeable components. It allows dynamic switching between payment methods, sorting algorithms, or authentication strategies without altering core business logic.

Key Components

Strategy Interface - Defines common operations for all algorithm variations
Concrete Strategies - Implement specific algorithms
Context Class - Maintains reference to current strategy

Implementation Example

Strategy Interface

// PaymentStrategy interface
class PaymentStrategy {
  constructor() {
    this.type = 'base';
  }

  pay(amount) {
    throw new Error('This method must be implemented');
  }
}

Concrete Strategies

class CreditCard extends PaymentStrategy {
  constructor(cardNumber) {
    super();
    this.cardNumber = cardNumber;
  }

  pay(amount) {
    return `Processed $${amount} via credit card ending in ***${this.cardNumber.slice(-4)}`;
  }
}

class PayPal extends PaymentStrategy {
  constructor(email) {
    super();
    this.email = email;
  }

  pay(amount) {
    return `Processed $${amount} via PayPal for ${this.email}`;
  }
}

Context Usage

Real-World Applications

💳 Payment Systems

Allow dynamic switching between payment methods
Support multiple payment providers without tightly coupling code

📊 Data Compression

Support various compression algorithms (gzip, zip, bzip2)
Allow runtime selection of compression level

🚀 Game AI

Implement different AI behaviors per game character
Easily switch between combat/defense strategies during runtime

Common Questions