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Facade Pattern

The Facade pattern provides a simplified interface to a complex subsystem. It reduces the complexity of the system by hiding the underlying implementation details.

When to Use:

Use the Facade pattern when you want to simplify the interface to a complex system.

Example

// Subsystem classes
class CPU {
  freeze() {
    console.log('CPU freezing...');
  }
  jump(position: number) {
    console.log(`CPU jumping to position ${position}`);
  }
  execute() {
    console.log('CPU executing...');
  }
}


class Memory {
  load(position: number, data: string) {
    console.log(`Memory loading data at position ${position}`);
  }
}


class HardDrive {
  read(lba: number, size: number) {
    return 'Some data from HardDrive';
  }
}


// Facade class
class ComputerFacade {
  private cpu: CPU;
  private memory: Memory;
  private hardDrive: HardDrive;


  constructor() {
    this.cpu = new CPU();
    this.memory = new Memory();
    this.hardDrive = new HardDrive();
  }


  start() {
    this.cpu.freeze();
    this.memory.load(0, this.hardDrive.read(0, 4096));
    this.cpu.jump(0);
    this.cpu.execute();
  }
}


// Usage
const computer = new ComputerFacade();
computer.start();

Pros:

  • Simplifies the interface to complex subsystems.
  • Promotes loose coupling between clients and subsystems.

Cons:

  • Can lead to the creation of overly simple interfaces that don’t offer enough flexibility.
  • May increase the complexity of the system if not used judiciously.

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