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An Introduction to JavaScript Proxy

The JavaScript Proxy object is a relatively new addition to the language, having been introduced in ES6. It's based on the software design pattern of the same name, which creates a wrapper for another object, intercepting and redefining fundamental operations for that object.

A Proxy object is defined as follows:

const proxy = new Proxy(target, handler);

The target is the object that the proxy wraps around, while the handler is an object that contains one or more "traps" - functions that intercept operations performed on the target object.

There are a variety of available traps that can be used to customize the behavior of the target object. Here's a brief overview of all available traps and what each one does:

There are many common and novel use-cases for the Proxy object, utilizing one or more of these traps. Here's a simple example that intercepts a get call and returns null if the property doesn't exist in the target object:

const targetObj = { name: 'John', age: 30 };

const handler = {
  get(target, property) {
    return property in target ? target[property] : null;

const proxyObj = new Proxy(targetObj, handler);; // 'John'
proxyObj.age; // 30
proxyObj.address; // null

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