Chain Of Responsibility

Purpose: Behavioural Type: Object


Used to achieve loose coupling where a request from a client is passed to a chain of objects to process them. The object in the chain will decide whether the request moves onto the next object in the chain or not.

Applicable when:

  • Decoupling request's sender and reciever
  • Multiple objects, determined at runtime, are candidates to handle a request
  • Don't want to specific handlers explicitly
  • Want to issue a request to one of several objects without explicitly specifying the reciever


  • Handler: An interface which will primarily recieve the request and dispatch that request to the chain of handlers.
  • Concrete handlers: Handlers that actually handle the request chained in some sequential order.
  • Client: Originator of request and will access handler to handle it.



  • Reduce coupling degree.
  • Flexible, simplified objct that does not need to know the chain structure.
  • Convenient to increase request processing.


  • No guarantee for request recieved.
  • Performance of system affected, but also code debugging may not be so easy and could by cyclical.
  • Observability of operation characteristcs not so easy.


class Handler { private _successor: Handler; public set successor(successor: Handler) { this._successor = successor; } public get successor() { return this._successor; } public handleRequest(msg: Number): void {} } class ConcreteHandlerA extends Handler { handleRequest(req: Number): void { if (req > 0) { console.log(`Handler A process ${req}`); } else { this.successor.handleRequest(req); } } } class ConcreteHandlerB extends Handler { handleRequest(req: Number): void { if (req < 0) { console.log(`Handler B process ${req}`); } else { this.successor.handleRequest(req); } } } class ConcreteHandlerC extends Handler { handleRequest(req: Number): void { if (req === 0) { console.log(`Handler C process ${req}`); } else { this.successor.handleRequest(req); } } } (function main() { const reqA = new ConcreteHandlerA(); const reqB = new ConcreteHandlerB(); const reqC = new ConcreteHandlerC(); // set the chain or responsibility reqA.successor = reqB; reqB.successor = reqC; // handle the requests reqA.handleRequest(0); // logs "Handler C process 0" reqA.handleRequest(1); // logs "Handler A process 1" reqA.handleRequest(-1); // logs "Handler B process -1" })();