JavaScript Design Patterns — Structural — Composite

The Composite pattern allows the creation of objects with properties that are primitive items or a collection of objects. Each item in the collection can hold other collections themselves, creating deeply nested structures.

In the example below, we create a computing equipment subsystem that is stored in a Cabinet. Each element can be a different instance.

// Equipment
class Equipment {
  getPrice() {
    return this.price || 0;
  }

  getName() {
    return this.name;
  }

  setName(name) {
    this.name = name;
  }
}

class Pattern extends Equipment {
  constructor() {
    super();
    this.equipments = [];
  }

  add(equipment) {
    this.equipments.push(equipment);
  }

  getPrice() {
    return this.equipments
      .map(equipment => {
        return equipment.getPrice();
      })
      .reduce((a, b) => {
        return a + b;
      });
  }
}

class Cabbinet extends Pattern {
  constructor() {
    super();
    this.setName('cabbinet');
  }
}
// --- leafs ---
class FloppyDisk extends Equipment {
  constructor() {
    super();
    this.setName('Floppy Disk');
    this.price = 70;
  }
}

class HardDrive extends Equipment {
  constructor() {
    super();
    this.setName('Hard Drive');
    this.price = 250;
  }
}

class Memory extends Equipment {
  constructor() {
    super();
    this.setName('Memory');
    this.price = 280;
  }
}

👉 Use this pattern when we want to represent hierarchies of objects.

🚀 A complete example here: https://stackblitz.com/edit/vitejs-vite-8eqxdx?file=main.js

I hope you found it useful. Thanks for reading. 🙏

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