As developers, we often come across situations where we need to add functionality or make modifications to objects or functions without directly modifying their code. This is where the concept of cross-cutting concerns comes into play. Cross-cutting concerns are functionalities that are required by multiple components in a system and can be implemented at a centralized place.

In JavaScript, we can leverage the power of the Proxy object, introduced in ECMAScript 6, to achieve this. The Proxy object allows us to intercept and customize operations performed on an object, such as reading, writing, or deleting properties.

Let’s take a look at an example to understand how we can use the Proxy object for cross-cutting concerns:

const car = {
  brand: 'Tesla',
  model: 'Model 3',
};

const carHandler = {
  get: function (target, property) {
    console.log(`Getting ${property}...`);
    return target[property];
  },
  set: function (target, property, value) {
    console.log(`Setting ${property} to ${value}...`);
    target[property] = value;
  },
  deleteProperty: function (target, property) {
    console.log(`Deleting ${property}...`);
    delete target[property];
  },
};

const proxyCar = new Proxy(car, carHandler);

console.log(proxyCar.brand);  // Output: Getting brand... Tesla

proxyCar.model = 'Model Y';   // Output: Setting model to Model Y...

delete proxyCar.brand;        // Output: Deleting brand...

In the above example, we have an object car representing a car with brand and model properties. We define a carHandler object, which contains the handler functions for the get, set, and delete operations. The Proxy constructor is then used to create a proxyCar object, which will intercept these operations.

Whenever a property is accessed or modified on the proxyCar object, the corresponding handler function will be triggered. In this case, we log the action being performed and then delegate the actual operation to the original object using target[property]. This allows us to add custom logic or perform side effects before or after the operation.

Using the Proxy object, we can easily implement common cross-cutting concerns such as logging, caching, validation, or even providing default values. By isolating these concerns in a centralized proxy object, we can avoid cluttering our core business logic and achieve cleaner and more maintainable code.

#JavaScript #Proxy