Chain of Responsibility

Chain of Responsibility is a behavioral design pattern that lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.

Usage

class Handler {
  constructor(nextHandler) {
    this.nextHandler = nextHandler;
  }

  handle(request) {
    if (this.nextHandler) {
      return this.nextHandler.handle(request);
    }

    return null;
  }
}

class ConcreteHandler1 extends Handler {
  handle(request) {
    if (request === 'request1') {
      return 'ConcreteHandler1';
    }

    return super.handle(request);
  }
}

class ConcreteHandler2 extends Handler {
  handle(request) {
    if (request === 'request2') {
      return 'ConcreteHandler2';
    }

    return super.handle(request);
  }
}

const handler1 = new ConcreteHandler1();
const handler2 = new ConcreteHandler2(handler1);

console.log(handler2.handle('request1')); // ConcreteHandler1
console.log(handler2.handle('request2')); // ConcreteHandler2
console.log(handler2.handle('request3')); // null

Chain of Responsibility

Usage

On this page