README.md

Proxy Pattern

The Proxy pattern is used to control access to an object by placing a surrogate or placeholder object (the proxy) in front of the real object (the real subject).

Example

class RealSubject {
  request() {
    console.log("RealSubject: Handling request.");
  }
}

class Proxy {
  constructor(realSubject) {
    this.realSubject = realSubject;
  }

  request() {
    if (this.checkAccess()) {
      this.realSubject.request();
      this.logAccess();
    }
  }

  checkAccess() {
    console.log("Proxy: Checking access prior to firing a real request.");
    // Simulate access check
    return true;
  }

  logAccess() {
    console.log("Proxy: Logging the time of request.");
  }
}

Explaining the code

1. RealSubject Class:

   • This class represents the real object that performs the actual work. It has a request method that logs a message indicating it is handling the request.

2. Proxy Class:

   • This class acts as a proxy to the RealSubject. It holds a reference to an instance of RealSubject and controls access to it.
   • The request method in the Proxy class first checks access by calling checkAccess. If access is granted, it forwards the request to the RealSubject and then logs the access by calling logAccess.

Usage

const realSubject = new RealSubject();
const proxy = new Proxy(realSubject);

proxy.request();

• An instance of RealSubject is created.
• An instance of Proxy is created, with the RealSubject instance passed to its constructor.
• The request method is called on the Proxy instance. This triggers the access check, forwards the request to the RealSubject if access is granted, and logs the access.

Summary

The Proxy pattern is used to control access to an object. In this example, the Proxy class controls access to the RealSubject by checking access and logging the request. This pattern is useful for adding additional functionality (like access control and logging) without modifying the original class.