Flyweight Pattern

The Flyweight Pattern is a structural design pattern that enables efficient sharing of objects to support a large number of fine-grained objects. This pattern is particularly useful in situations where memory usage is a concern and you want to minimize the overhead of creating numerous similar instances.

• Flyweight: The core object that encapsulates shared state.
• Intrinsic State: The state that can be shared across multiple objects.
• Extrinsic State: The state that is unique to each object and cannot be shared.

Use the Flyweight Pattern when:

• Many objects share similar states.
• The cost of creating new objects is high.
• You want to minimize memory usage.

Step 1: Define the Flyweight Class

class Flyweight {
    constructor(intrinsicState) {
        this.intrinsicState = intrinsicState; // Shared state
    }

    operation(extrinsicState) {
        // Use intrinsic state and extrinsic state
        console.log(`Intrinsic: ${this.intrinsicState}, Extrinsic: ${extrinsicState}`);
    }
}

Step 2: Create a Flyweight Factory

class FlyweightFactory {
    constructor() {
        this.flyweights = {};
    }

    getFlyweight(intrinsicState) {
        if (!this.flyweights[intrinsicState]) {
            this.flyweights[intrinsicState] = new Flyweight(intrinsicState);
        }
        return this.flyweights[intrinsicState];
    }
}

Step 3: Use the Flyweight

const factory = new FlyweightFactory();

const flyweight1 = factory.getFlyweight('State1');
flyweight1.operation('Unique1');

const flyweight2 = factory.getFlyweight('State1');
flyweight2.operation('Unique2');

console.log(flyweight1 === flyweight2); // true, same instance

Consider using Flyweight when the application is expected to have a high number of similar objects, such as in graphics rendering, text formatting, or similar scenarios.