Strategy Pattern

Algorithm Encapsulation

GitHub Link: https://github.com/FrancescoXX/Design-Patterns-Strategy-Javascript

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Behavioral Design Pattern

Intro

The Strategy pattern, also called policy pattern, enables selecting an algorithm at runtime.
Deferring the decision about which algorithm to use, allows more flexibility and reusability

⚡️Recognize

When we want to change the behavior of our application at runtime

For example, change the behavior to:

• aggressive
• defensive
• balanced

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💡Intent

• Define different algorithms
• Make them interchangeable at runtime, with a setStrategy() method

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🔧 Apply when

• Classes only change in behavior
• We want Different variants of an algorithm

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✅Pro

• Algorithm families use inheritance for common parts Avoid conditional statements using this pattern Clients can choose the required behavior

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⚠️Cons

• Increased number of objects
• Strategies are shared between objects

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🏆 Great for

• Encapsulate an algorithm
• Change algorithm at runtime

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/**
 * STRATEGY PATTERN JAVASCRIPT IMPLEMENTATION
 */

//Concrete Strategy A
class AggressiveStrategy {
    constructor() {
        this.next = move => "Next aggressive move";
    }
}

//Concrete Strategy B
class BalancedStrategy {
    constructor() {
        this.next = move => "Next balanced move";
    }
}

//Concrete Strategy C
class DefensiveStrategy {
    constructor() {
        this.next = move => "Next defensive move";
    }
}

//Strategy
class AIGameStrategy {
    constructor() {
        this.setStrategy = (game) => this.game = game;
        this.next = move => this.game.next(move);
    }
}

// --- MAIN ---

//Strategies initialization
const aggressive = new AggressiveStrategy();
const balanced = new BalancedStrategy();
const defensive = new DefensiveStrategy();

//Implement Strategy Pattern
const AI = new AIGameStrategy();

//Set Defensive Strategy
AI.setStrategy(defensive);

//Perform defensive action
console.log(AI.next()); //Next defensive move

//Set Balanced Strategy...
AI.setStrategy(balanced);

//Perform balanced actions
console.log(AI.next()); //Next balanced move
console.log(AI.next()); //Next balanced move
console.log(AI.next()); //Next balanced move

//Change Strategy to Aggressive
AI.setStrategy(aggressive);

//Perform aggressive actions
console.log(AI.next()); //Next aggressive move
console.log(AI.next()); //Next aggressive move

GitHub Link: https://github.com/FrancescoXX/Design-Patterns-Strategy-Javascript