Javascript proxies

What are proxies?

Proxies are a powerful feature that allows you to intercept and customize operations on objects. They are a way to create a custom behavior for fundamental operations (e.g., property lookup, assignment, enumeration, function invocation, etc.) on objects.

Proxies are created using the Proxy constructor, which takes two arguments: the target object and a handler object. The target object is the object that the proxy wraps, and the handler object is an object that defines the custom behavior for the proxy.

Here is an example of creating a simple proxy that logs property access:

const target = {
  name: 'Alice',
  age: 30
};

const handler = {
  get: function(target, prop, receiver) {
    console.log(`Getting property ${prop}`);
    return Reflect.get(...arguments);
  }
};

const proxy = new Proxy(target, handler);

console.log(proxy.name); // Logs: Getting property name
console.log(proxy.age); // Logs: Getting property age

In this example, the handler object defines a get trap that logs the property being accessed. When we access the name and age properties of the proxy object, the get trap is triggered, and the property access is logged.

Why use proxies?

Proxies are useful for a variety of use cases, such as:

• Logging and debugging: Proxies can be used to log property access, assignment, and function invocation for debugging purposes.
• Validation and type checking: Proxies can enforce constraints on object properties, such as ensuring that a property is of a specific type or that it meets certain criteria.
• Security: Proxies can be used to restrict access to certain properties or prevent certain operations on objects.
• Data binding: Proxies can be used to create reactive data structures that automatically update when their properties change.