JavaScript Proxy

A JavaScript Proxy serves as a intermediary object, allowing developers to intercept and customize fundamental operations on objects. Think of it as a guardian standing between your code and the object it interacts with, granting you unprecedented control over the behavior of the target object.

In the below PDF we discuss about Javascript Proxy in detail in simple language, Hope this will help in better understanding.


Creating a Proxy:

To create a Proxy, you use the Proxy object, passing in two arguments – the target object and a handler object. The target object is the object you want to wrap with the proxy, and the handler object contains methods (known as traps) that define the custom behavior for various operations.

The Syntax of Proxy is:

new Proxy(target,handler):
  • new Proxy() – the constructor.
  • target – the object/function which you want to proxy
  • handler – can redefine the custom behavior of the object

For Example,

// Target object
const targetObject = {
name: 'John',
age: 25,
// Handler object
const handler = {
get: function (target, prop) {
// Custom behavior when getting a property
console.log(`Getting property: ${prop}`);
return target[prop];
// Create a Proxy
const proxyObject = new Proxy(targetObject, handler);
// Accessing a property triggers the custom behavior
console.log(; // Output: Getting property: name, John

In the example above, we’ve created a simple proxy that logs messages whenever a property is accessed or modified.

Uses of Proxy:

  1. Validation and Security: Proxies can be used to enforce constraints on object properties, providing an additional layer of security. For instance, you can ensure that certain properties are read-only or prevent specific properties from being deleted.
  2. Logging and Debugging: By intercepting property access and modification, you can implement powerful logging mechanisms for your objects. This is particularly useful for debugging and understanding how your code interacts with different parts of your application.

Related Question

JavaScript Proxy is an object that allows you to intercept and customize the fundamental operations on another object, such as property access, assignment, invocation, etc.

You can create a Proxy using the Proxy constructor. It takes two parameters: the target object to proxy and a handler object that contains methods to customize the proxy’s behavior.


Yes, you can. For example, you can use the set trap to enforce validation rules when setting properties. If a validation condition fails, you can throw an error or handle it in a custom way.

Yes, Proxies come with some considerations, such as potential performance overhead due to the interception of operations. Additionally, not all operations can be trapped, like the in operator for property existence.


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