Introducing JavaScript Proxy

A JavaScript Proxy is an object that allows you to intercept and customize operations performed on other objects. It acts as a middleman between the calling code and the target object, enabling you to control and manipulate the behavior of the target object. 

Proxies are particularly useful for handling scenarios such as data validation, logging, security, and caching. For instance, if you want to validate the data before it is assigned to an object property, you can use a proxy to intercept the operation and perform the validation.

In order to create a proxy object, you can use the built-in Proxy constructor in JavaScript. The constructor takes two arguments: the target object and a handler object. The handler object defines the methods that will be called when certain operations are performed on the proxy object.

Here are some of the methods that can be defined in the handler object:

- get: called when a property of the target object is accessed.

- set: called when a property of the target object is set.

- deleteProperty: called when a property of the target object is deleted.

- apply: called when a function of the target object is invoked.

Let's take a look at an example of creating a proxy object that intercepts the set operation on a target object:

```

const target = {};

const handler = {

  set: function(obj, prop, value) {

    console.log(`Setting value '${value}' to property '${prop}'`);

    obj[prop] = value;

    return true;

  }

};

const proxy = new Proxy(target, handler);

proxy.name = 'John'; // Setting value 'John' to property 'name'

console.log(target.name); // John

```

In the example above, we define a handler object with the set method that logs the property name and the assigned value to the console. When the `proxy.name = 'John'` statement is executed, the set method is called and the output is logged to the console. The property `name` is then set to the value `John` on the target object.

Overall, JavaScript Proxy is a powerful feature that can be used to implement a variety of advanced programming techniques. By using a proxy, you can customize and control the behavior of an object and perform operations such as validation, logging, security, and caching.